My point is atheists don't "preach," at least in the sense of preaching the Word. Certainly we can get up and pontificate endlessly and not be fun at parties, same as everybody else about every subject. But I interpreted your remark as you falling into the fallacy that atheism is "just another faith," which has been refuted here many times by myself and others.
Now, to your barb: anybody can commit mass murder. First, anybody can be insane, but that's boring.
Second, anybody can be sane but seduced by an ideology.
Atheism is typically a healthy antidote to ideological fanaticism. An atheist living in a theist society can hardly fail to notice the perils of being on the wrong end of socially- and institutionally-transmitted blindness and ignorance. But atheists, while on the whole (certainly not one-for-one) likely smarter or at least more curious than theists, do not escape the unpleasantness at the bottom half of the bell curve. The more limited ones can have the silicon chip inside their head switched in much the same way as a religious fanatic would, and like him decide the gene pool needs some chlorine.
