Why do people have to verbally attack other religions so much?

I've joined Yahoo! Answers a few hours ago and while browsing through questions there seemed to be a common theme in which people have a need to say christians are stupid/brain washed, catholics need to be shot, blatantly state their god doesn't exist (theres nothing wrong with that but >>>) and... show more I've joined Yahoo! Answers a few hours ago and while browsing through questions there seemed to be a common theme in which people have a need to say christians are stupid/brain washed, catholics need to be shot, blatantly state their god doesn't exist (theres nothing wrong with that but >>>) and then insult and slander them so much that you have to scroll down to read the rest of their comment (maybe just little bit exagerated ^_^, but you get the picture.)

I know that i've only mentioned christians because thats the only type i've seen but im sure other religions share this problem, which I'll have to look into.

Anyway, /why/ is it that people have to 'attack' other religions, even those who don't follow a religion seem to need to do this. I mean why can't we just accept that people beleive different things and then point out why we dont share their beliefs, nicely, rather then mock and insult them? (I know not everyone does this)

(If it helps you, im christian)
Update: Edit - Sorry if it wasn't clear, I didn't say christians don't do any of the above and im sure that many actually provoke other people, but I guess that somewhere its got to start to settle down.
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