///Do most people who call themselves atheists not just do it as an excuse to argue with Mormons and Jehovah's Witnesses at the front door?///

I don't know. I won't answer my door unless I know who it is that's knocking (yes, I even removed the buzzer) but you said "most" atheists so I can't speak for the rest. In reality, I don't argue with anybody about this topic because nobody has actually told me that I must believe in god. I just think the counterarguments are good to know for your own edification.