Just like any other group of humans. I knew one Muslim who had no problem with atheism. He was well-educated and generally liberal. Except on the subject of adultery - for that, he wanted the traditional
sharia penalty imposed on both parties - death. I have no idea if that was because of some personal experience, but I doubt it. I went to his wedding, where he married his first wife.
Knew another guy who spent some time in the US, and fell head-over-heels for an American woman. He was already married and actually mulled over the idea of making her his second wife...which he could theoretically do under Islam. Oh, almost forgot the punch line - that woman he fell for? She was Jewish. I can't even imagine the complexity of that problem, even if she was a "secular" American Jew. AFAIK, spouses who marry Muslims are still absolutely required to convert.
I knew a couple in Saudi Arabia who faced that problem, except the husband was an atheist. The bride's father insisted he convert to Islam, so he did. But he never meant it for a second. His wife didn't seem to have any problem with that. Lovely couple and the two of them made some excellent homemade brandy. Tasted a lot like Courvoisier.
So just an example - several different Muslims, several different ways of thinking.
Total change of subject - to understand modern radical Islam, I think one good place to start is Sayyid Qutb.
And you should probably start with
Fi Zilal al-Quran (In the Shade of the Qur'an) - his 30-volume commentary on the Koran.
Just kidding. Qutb spent some time in the United States, and it didn't liberalize him a bit - the experience horrified him. Especially the open mixing of the sexes, and the way uppity women went around wearing whatever they wanted. He was especially outraged when he went to a dance held IN A CHURCH and couples were slow-dancing together!
Strictly IMO, as always, but I think just about every current seed of radical Islam sprouted from Qutb's fields of bullshit.
http://en.wikipedia.org/wiki/Sayyid_Qutb