Why is it that when we get into a heated discussion with Christians they think that because we are upset that it proves that they are correct in their beliefs? They say things like "Well, you're the only one upset. I'm not upset. I'm not forcing my religion on you. Why are you trying to force me?." As if to say, "Well, that proves that my god exists because you are trying to get me to see things your way and I can't be swayed. So now you are aggravated, which proves I'm right." It is really patronizing! Also, any advice would be great on how to deal with people like that would be helpful.

It's a rhetorical trick: the first person to get flustered is "wrong". It's a bogus mind game.

I see another version of this, where they conclude that I'm "mean" because I'm pointing out unpleasant facts about their religion. If I'm "mean", I must not be right (or worth listening to). This is also a mind game. When I can, I tell those people that most Christians believe that atheists deserve to be tortured for all eternity (for using their brains) and THAT is the epitome of meanness and misanthropy. They never see it that way--they think they're all angels and we should be just like them.