Now I understand the realpolitik behind such statements but in this instance and in the way this was phrased it is less than helpful .
It’s also self-evidently wrong. Whether or not ISIS conform to Cameron’s view of what Muslims should be the Jihadists self-identify as Muslims and moreover consider themselves to be the true face of Islam. Also, trivially, if they are not Muslims what are they? Perhaps Anglican heretics or lapsed Catholics or maybe they kill to the glory of L. Ron Hubbard and we’ve just mistaken their battered copies of Dianetics for the Qur’an.
“Muslim or monster” is a puerile and dangerous juxtaposition to make. They are not mutually exclusive any more than Christian and monster or Hindu and monster are as it is perfectly possible to be both a follower of a faith and a monster. It plays into the false idea that to be religious is to be moral and that the truly devout cannot behave immorally
All religions are religions of peace to those who follow them peacefully and all are capable of being justifications of violence to those who would be violent (although I maintain that Islam has peculiarities which make radicalism easier to justify). The extent to which the majority of Muslims are “good” is, I suggest, precisely the extent to which people in general are “good”. I would expect most human beings to find moral outrage in the behaviour of ISIS regardless of their religious allegiances and I would expect the majority of Muslims to condemn them as not being representative of Islam. But to suggest ISIS are not Muslims is absurd and a blatant use of the No True Scotsman logical fallacy.
I get that western politicians are anxious not to demonise Muslims in general and they are right to do this. Muslims in general are not demons or any other kind of monster but pretending that radical islamists are not Muslims at all is to neglect a great deal of the ideology that motivates them. Neither will a white Middle England Anglican telling a potential British jihadist that they are doing Islam wrong persuade them from heading to Syria. If anything it will be a greater motivation.