I want to beleive that you have the right to say anything you want, that you shouldn't worry about upsetting someone, even if it's too polemical, but... I agree with your friend about it being too risky :/ If there are violent extremists in your area I would suggest you consider leaving that out of the book.
I guess in my mind I'm comparing this to the problem with drug-dealers here in my city, it's not the same of course, what I mean is that people get threatened, kidnapped or attacked just for writing articles on the newspaper or talking wrongly about them in college classrooms... If extremists groups can be as violent as this people, well... :/
Of course, this is just my local situation.
On the other hand, I have seem some polemical works about christianity receiving just harsh comments or bans in a country that is very traditional like Mexico, and nothing worse than that, so...I don't know, I guess it all depends on your local situation.
....My own little frustration of the moment is that I'm stuck babysitting again, ha
EDIT: AND the kids just scratched my Wind Waker cd very badly.... shit, that intro is not loading properly...