A common problem faced today, especially with “religious violence” on the rise, is what it means to be religious – or rather to belong to a religion. “Being” of a religion has some rather fuzzy lines – are any mistakes allowed? who has the power/authority to claim that another person is no longer part of the faith? what sources can be used to justify such claims? how do we avoid creating additional schisms within religious communities or worse, the persecution of the “out” groups?
These are relevant questions, precisely because so much of the “religious violence” is at least partially premised on groups like ISIS declaring people who do not agree with them to be non-Muslim (a process called takfeer), and thus justify their indiscriminate murder rampages. They are also pertinent because we don’t like apparent contradictions in definitions. A person claiming to be an atheist can’t very well pray to God, neither can a pacifist willingly engage in violence – it’s a contradiction in terms. Simply claiming that groups like ISIS are themselves not Muslim feeds into the problem, and makes the excommunication of others a viable option for their use. Additionally, this kind of simple writing-off of people, groups, and ideologies is commonly taken to be a logical fallacy – specifically the “No True Scotsman” fallacy.
The No True Scotsman fallacy is described by logicalfalacies.info as:
a way of reinterpreting evidence in order to prevent the refutation of one’s position. Proposed counter-examples to a theory are dismissed as irrelevant solely because they are counter-examples, but purportedly because they are not what the theory is about.
This leaves us in a bind: we have a group of people clearly acting against the ideology they supposedly support, but if we excommunicate them, we feed into their excommunication agenda. On the other hand, if we don’t excommunicate them, then we’re agreeing that acts directly contrary to an ideology are compatible with that ideology. Damned if you do, damned if you don’t.
The problem, it should be noted, is somewhat peculiar in its inability to provide us with a clear definition who does and does not belong in a group. If I were to claim to be the Pope, the claim could easily be checked against a very concrete set of definitions, and the world would agree that I am not, in fact, the Pope. The same holds for the Dali Lama, or even specific religious orders – such as monks, etc. However, for simple religious adherents, the problem arises, precisely because the definition is relatively loose, and/or depends on the internal beliefs of a person – since the external claims are easy to make.
The way to address this issue is to challenge its premise; that is, to ask whether the only two options available to us are excommunication or affirmation. By not accepting the binary position, we get some working room, and it’s there that the solution can arise.
If we turn our focus away from the label of a person, and towards the label of an act, we can start to resolve this issue. By leaving aside the question of the person’s belief, we are not looking to excommunicate them. Instead, we focus on whether their actions fit within the ideology of the system in question – a question that is both easier to answer objectively, and one that does not result in the kinds of problems noted in the beginning.
For example, Bob claims to be a Muslim. We know this, because he says he is Muslim, and he pronounces the Islamic declaration of faith (shahada): There is nothing worthy of worship but God, and Muhammed is the Messenger of God. That’s all the external validation we need for the claim. The only way we can refute the claim is by being able to peer inside Bob’s mind, and extract his “true” intent – which is still beyond our scientific capacity.
Now, if Bob prays the obligatory prayers, gives the obligatory tax, fasts Ramadan, and tries to go to Hajj, he is exhibiting the kinds of acts that are defined as acts of a Muslim by the primary Islamic texts. Thus, we would conclude that those acts are within the realm of Islamic behavior.
If Bob steals, cheats, murders, rapes, and breaks contracts, he is exhibiting the kinds of acts that are defined as prohibited acts (not allowed to Muslims) by the primary Islamic texts. Thus, we would conclude that those acts are outside of the realm of Islamic behavior.
As a consequence, we can assess Bob as follows: Bob claims to be Muslim and some of his behaviors are within the realm of Islamic behavior, while a number of his behaviors are condemned by Islam. As a result, the Islamic position would consider Bob to be a wanted criminal, who should stand trial for the crimes he is accused of – and if found guilty, should be punished appropriately. The key point is that the behaviors themselves are clearly defined in the primary texts, and have been further elaborated (brought up to date with the modern situation) by a jurisprudential tradition that has very clear-cut system of qualifications for making legal statements and procedures for interpretation.
This seems to cover a number of actions that so many find so repugnant about actions of certain groups, and which seem to otherwise qualify them for excommunication. However, what about a more direct contradiction, on the order of a violent “pacifist?”
Here, we have to recognize that, despite certain ambiguities regarding what makes a religious adherent part of the religious group, there are some objective standards that can still apply. A monk who has taken the vow of chastity invalidates that vow by intentionally engaging in sexual relations; a person who claims to believe in Allah as a singular deity invalidates that claim by praying to anything other than Allah.
In these cases, we still want to stay away from excommunication. Instead, it seems more fitting to say that the person is mistaken about their claim, because their actions are in apparent contradiction to the claim. You’ll note that there are two terms in that statement that soften it: “mistaken” and “apparent.” The reason for this softening is precisely to stay away from excommunication, and give the claimant the benefit of a doubt – owing to perhaps a misunderstanding, an oversight, lack of mental faculties (generally or at the time), or any kind of an extenuating circumstance.
It may seem somewhat silly to keep this doubt extended indefinitely. However, by doing so, we avoid the noted problems. We also remove excommunication as a legitimate tool, and thus deny it to those who would seek to normalize its use from our own (let’s assume justified) use. However, that does not mean that the extension of doubt should be understood as condoning the act. On the contrary, the act is condemned theologically, and may be condemned legally (depending on the kind of action). However, this condemnation bypasses the sphere of internal belief and intent, and remains focused exclusively on the verifiable actions, which can be objectively judged.
Consequently, instead of calling ISIS members non-Muslims, we call their actions contrary to Islam, and consider them to be criminals to be brought to trial. Similarly, the Myanmar Buddhists that are engaged in the apparent genocide of Muslims are not non-Buddhists; their actions are contrary to Buddhism and they should be considered criminals to be brought to trial. Finally, we should beware the excommunication line because it allows people to engage in historical revisionism and cherry-pick only positive elements of whatever group they associate with – presenting a false front, and refusing to acknowledge and/or take responsibility for the not-so-bright parts of their group’s history.
By challenging the binary premise of using excommunication or validating atrocities, we’re able to get a better vantage point, and recognize the inherent problem of this : it requires us to either claim knowledge of people’s intentions or to disregard all definitions. If we turn to the objective analysis of actions, however, we bypass the false dichotomy and arrive at a functional system of rejecting unacceptable behavior, preserving objective definitions, and avoiding claims of knowing the intentions of people.
By challenging the binary premise of using excommunication or validating atrocities, we’re able to get a better vantage point, and recognize the inherent problem of this false dichotomy: it requires us to either claim knowledge of people’s intentions or to disregard all definitions. If we turn to the objective analysis of actions, however, we bypass the false dichotomy and arrive at a functional system of rejecting unacceptable behavior, preserving objective definitions, and avoiding claims of knowing the intentions of people. 
Yes, this may place us in the uncomfortable position of having criminals who claim to be part of our group. On the other hand, it is far more honest to speak about Muslims, Christians, Buddhists, etc. who are engaged in criminal behavior, than to pretend that these people are somehow entirely unrelated to the groups. A perversion of an ideology requires an ideology to be perverted – it does not simply fall from the sky. By refusing to engage in the excommunication/acceptance game, we also reveal the fact that every group, in every period, is made up of actual people; i.e. imperfect individuals, who may try to use whatever ideology for their own purposes.
This makes the ideological perversion a universal problem. Recognition of this fact does far more to properly separate between Islam and ISIS, or Buddhism and Myanmar’s genocidal regime, than excommunication efforts ever could. The recognition of individual perversion of ideology, once understood in a universal way, allows us to both differentiate between the ideology and actions of individuals, and gives us a better vantage for recognizing, anticipating, and fighting these positions, by getting at the roots of the perversion, rather than imagining that there is something magical about Islam that allowed ISIS to arise, or about Hinduism that allowed the rise of Tamil Tigers, or about atheism that allowed for the purges of Stalin and Mao.
 Incidentally, this is also the Islamic legal approach, partially due to the fact that it is Islamically prohibited to assert that another person is or is not a Muslim. Only the individual can make that claim for themselves; and the job of the theological and legal spheres is to worry about the permissibility/legality of individual acts, not belief.