Do you think atheists know why they do it?

I am not a Christian, nor am I an atheist (I guess I am agnostic). I was brought up in a Christian home, but I just have a hard time believing in organized religion or the Bible. That being said, I think that atheists who act like this are disgusting and should learn to keep their mouths shut, but I also need to say that I have met many Christians who do the exact same things, just on the opposite end of the spectrum. Each group has some of "those" people. I try not to let them influence me (from either point of view) because they all sound like idiots.