People will find any number of reasons for division and supposing religion didn't exist they'd be killing each other for being different shades of brown, for coming from a different family, for being born in a particular village. Sad but true.
I should of course point out that I am not in any way excusing what was done in the name of Islam, and nor am I denying that Islam in particular has a long and apparently "theologically justified" history of treating non-Muslim human beings as nothing better than animals; on the other hand, anti-theistic regimes have done just the same things using Darwinism as their god, with the justification of "science". People will justify their hate using any means at all.
I am quite sure that the majority of Muslims in this country and possibly worldwide are perfectly decent and compassionate people who are every bit as horrified at the act in question as I am; whether they're being entirely true to their own religion in that I can't say with any certainty.
I think religion in itself can make people hate eachother.
Of course some groups abuse religion to accomplish their agenda, and these groups would abuse whatever theory, belief, etc. possible to accomplish their goals. However, sometimes it is just religion in itself that causes hatred and although I stand for the right of everyone to believe whatever they want, I think a world without religion would be a better one.
Good comedians have to reject religion, because to be a good comedian you can't be retarded.