Hmmm...bit of an overstatement in that title, wouldn't you say? I mean, I'm an atheist...but I don't wear it on my sleeve. In fact, there are, I would imagine, few that actualy know of my beliefs, or the lack thereof. I bring it out when I feel that it is either necessary, or apropriate. To me, a fanatic describes someone that is all consumed by their beliefs, convictions, loyalties or emotions. My belief system does not include a "god". That one simple part of my makeup does not, I believe, consume me.
I think that you may be falling into the trap of claiming atheism to be a religion of itself. It is not. Rather it is the lack of a religion. You believe in God. I do not. You have religion. I do not. It's all really rather simple.
To be fair, though, I do know that there are some of my ilk out there that like to "preach", much as a born again ultra-Christian would. I would submit that those are the atheists that are trying to convince themselves, moreso than you, of the nonexistence of a deity. But most of us, I think, have made our own peace with our convictions....long ago. So, do me a favor and be careful of that broad brush with which you want to paint us.