Why do Halo fans and GOW fans hate each other?

well, i have been on the net lately (everyone here has) and I've heard a few things... power rangers in space... anyways, i know that there should be competition between these (awesome) games, but why do GOW players say things like 'the first person to say Halo should kill their self' in response to a question about good 360 games... there both amazing games (I think halos story is a little deeper but thats just me). I kinda prefer Halo but that might be because i had it first. they are both must haves to the 360, great games, and fun shooters... power rangers in space!?!? if your here to post anti halo/GOW then go away no one likes haters.