No True Scotsman
The No True Scotsman fallacy is a kind of Logical fallacy where the speaker attempts to salvage a generalized claim by qualifying it and restating in some way, simply in order to escape the objection that the generalized claim is false.
Suppose Angus says that "No true Scotsman would put sugar on their porridge". Someone objects that his uncle Hamish puts sugar on his porridge. Angus objects: "That just shows your uncle is no true Scotsman".
The fallacy is only relevant in cases where the subject of the generalization is vague or unclearly defined in the first place. If Angus claims that 'no vegetarian eats meat', you cannot object that your uncle Hamish is a vegetarian, and eats meat. Since the definition of a 'vegetarian' is one who does not eat meat, it is clear that Hamish cannot be a vegetarian.
Defining 'True' Islam
To some, the problem of defining the subject of generalization is particularly acute in the case of religions. Most religions have many factions, each of which believes that they are the 'true' version, and that the other factions are unbelievers.
Suppose Aazim says 'Muslims abhor violence'. Jake objects 'But Osama bin Laden does not abhor violence'. Aazim replies 'Osama bin Laden is not a true Muslim'. How do you judge who is correct?
One position many people take is to allow self-identification: if you say you’re a Muslim, you’re a Muslim, and bin Laden says he is a Muslim. So both interpretations are accepted as equally valid.
However, the easiest way to answer the question is to refer to the original sources, the Qur'an and Sunnah which tell us how Islam was practiced during, and directly after, the life of its founder, Prophet Muhammad. If Islam supported violence from its inception, then to argue against this would be to argue against the very foundation of the faith.
Rida acknowledges that this conception (the duty to kill every non-believer during the jihad) may have been understood in the past, and may even now be common among the ignorant or less educated Muslims, but is a mistake.
However, W.R. Gardner, a Christian theologian and scholar of the Qur'an and Sufism, has refuted such apologetic 'reinterpretations' of jihad war:
There is undoubtedly a feeling, if not a belief, among many Westerners that a Moslem regards it as a duty binding on him in accordance with the literal command of the Koran, to kill any and every unbeliever whom he may meet when once jihad has been proclaimed. Sheikh Rid acknowledges that this conception of the duty of a Moslem during jihad may have been in the past, and may even now be that which is common among the ignorant or less educated Moslems... among the more recent Moslem apologists, jihad is regarded as war in defence [sic] of Islam, but we have been forced to the conclusion that any war in which a non—Moslem power is the aggressor must inevitably be regarded by Moslems as involving on their part jihad. The point we have now to consider is, what is the teaching of Mohammedanism as to wars of aggression. Is a war for the extension of Islamic rule also jihad ? In considering this point, not much light is to be got from the writings of the more recent Moslem authors, such as those we have quoted. They simply deny that it is a principle of Islam that jihad may include wars of aggression. By denying this, however, they do not prove anything; and, in order to get light on this part of the question before us, we must look at the Koran itself through those explanations of it which up to the present time pass as authoritative. This does not, of course, mean that these explanations are necessarily correct. Maulavi Chir gh 'Ali, for example, denies that they are correct. To quote his opinion as given in Sell's 'The of Faith of Islam,' p. 411, 'All fighting injunctions in the Koran are, in the first place, only for self—defence, and none of them has any reference to making war offen sively. In the second place, they are transitory in their nature. The Mohammedan Common Law is wrong on this point where it allows unbelievers to be attacked without provocation.' We do not desire here to discuss this question as to whether the Common Law is right or wrong, that is, whether orthodox Mohammedanism is a fine representation of the spirit and teaching of the Koran, or whether a better and truer representation of the conception of Mohammed and of his teachings might not have been given in a system of doctrine, developed from the point of view of Maulavi Chir gh `Ali and such Moslems as he...Let us quote his words again: 'The Mohammedan Common Law is wrong on this point when it allows unbelievers to be attacked without provocation.' We take then as proved, the statement that Mohammedan Common Law allows unbelievers to be attacked without provocation... 
- Logical Fallacies - A hub page that leads to other articles related to Logical fallacies
- Qur'an, Hadith and Scholars
- No true Scotsman - Wikipedia
- W.R. Gardner. 'Jihad', Moslem World, Vol. 2, 1912, cited in, A.G. Bostom. The Legacy of Jihad, Prometheus Books, Amherst, N.Y., 2005, p.295.
- Bostom. The Legacy of Jihad, pp.294, 297—299