The question strikes me as too vague and almost unanswerable (except by inference and guessing, see below) as written.
What people do you mean?
And what do you mean by those words – are you referring to the book @elbanditoroso just mentioned?
Surely there are many people who would or wouldn’t find just about anything offensive or not.
For example, I’m not offended by that book because I have not read it, and don’t see anything offensive about what I skimmed of it. There are also blurbs from two other people who say they liked the book, apparently not offended. Also, I see you wrote “anti religion” and I think the author is Jewish (though that could just mean ethnically, and I ran out of curiosity to do more research to find out).
If you are postulating (?) what if someone wrote a book with the same synopsis and similar title, but they were “an anti religion, anti muslims person”, then I can imagine myself learning about this hypothetical book and either not being offended, or being offended, depending on what the book was actually like.
That is, even “an anti religion, anti muslims person” could write an inoffensive book. (And even inoffensive people writing innoffensive books manage to offend some people.)
But, guessing further, perhaps wildly inaccurately, at what you might mean, I do find that there is an entire class of expression on the Internet, which involves attempting to stir up xenophobia and hatred towards Muslims of various types, by posting limited perspectives and/or exaggerations of stories and conditions involving such people, and I often to find those to be offensive and upsetting.
The reason such things offend and upset me is that they seem to me to be nasty manipulative dehumanizing reductionist dangerous xenophobic hate-mongering, attempting to perpetuate, reinforce, and increase the already-inappropriate labeling of Muslims as all being dangerous hostile “others”, which seems to have been used as an excuse for great amounts of misguided violence, prejudice, maltreatment and suffering.