It isn’t about “defense of evil”. Brainwashing (conditioning) is a fact of life - we see it everywhere & at least to some extent.
As a very small example, take McDonalds’ ads on tv, before “healthy choices” were put on the menu. If you were constantly & only exposed to those ads from childhood, didn’t know any better, were told McDonalds is good for you, were rewarded for eating only McDonalds, and were threatened to be punished or actually were punished for not eating McDonalds, then by the time you reach adulthood you’d be conditioned. Think of Islam & what it teaches the same way, only with greater depth & breadth of brainwashing. Of course, moslems may end up being either repulsed by it or sink deeper into its depth.
Naturally, the ability to make choices, once one reaches adulthood will always exist, regardless of consequences.
If McDonalds was going around chopping heads off and so on for eating someplace else, then you’d have a point.