When people learn you are an atheist, there will be misunderstandings at a level beyond the ordinary misunderstandings in communication that happen all day long anyway. There will also be unwarranted emotional responses, and often a large display of outright ignorance. Most of the time, these misunderstandings have been slight. Well, I think they are slight. I tend to test the emotional waters, and if things haven't gone South, I don't care that much. But I avoid calling attention to my atheism because I don't like being misunderstood. Lord knows, I don't understand religious people. When I'm in a large group of them, it's like being in an asylum, where inmates wander around in their own little worlds, mumbling crazy thoughts while being completely disconnected from each other.
In cases where there is a lot of preaching going on, I have left. I've listened to this stuff my entire life and decided that it's worthless crap. I start feeling like I'll scream if I am forced to listen to a steady stream of such incoherent gibberish. I become part of the asylum myself. I need to seek out a place where I can talk with someone about more meaningful or normal things, the weather, how much they love their dog, or filing my tax return.