So the next time someone tells me they believe in God, I'll say "Oh, that's cool" and then change the subject.

Honestly, the people in my life that matter - their religious or spiritual beliefs do not matter when it comes to my relationship with them and I realize that's not the case for everyone. But if I'm talking to a complete stranger or acquaintance, why am I trying to incite an argument... because that's exactly what this is doing; trying to elicit an emotional response. When bringing this kind of crap up you really have to consider "to what end?". Chances are you're not Richard Dawkins giving a lecture at a university. You're having/starting a pissant little argument with someone that doesn't matter. If a religious person is asking why you don't believe in a god then state your logical reasoning. IF they give you shit, then defend yourself. Most people come to the no god conclusion on their own and a lot never ever will/do. Make your stance in the settings where it matters like when some type of group or legislation is threatening to violate the separation of church and state or trying to get religion in the classroom.

I'm only saying this from experience of alienating myself from my peers because I had to make the logical stance like I was going to prove to them how they are wrong and they're beliefs don't make sense. I still full heartedly believe their beliefs are lunatic, I just don't give a shit to try and convince them anymore. They aren't walking away with "oh man, I guess he's totally right" they're thinking "that guy is an insensitive asshole, he needs faith in jesus. i will pray for him". People come to these understandings on their own terms and there's a huge difference between attacking beliefs and defending the truth.