Preaching atheism as a religion. Aggressive atheists often do this a lot. Oddly enough, the most targeted religion is always Christianity, even though there are so many religions out there with skeletons in the closet. This trait can sometimes be traced back to a religious upbringing; many atheist evangelists are often disgruntled ex-Christians, hence explaining their bias. Anti-Christian zealot is probably a better word, I've met people who rant and rave about Christianity and claim to hate all religion but practice buddhism because they think it is some sort of "perfect religion".

Many anti-Christian "atheist evangelists" I know have not read the bible, instead making wide-sweeping and generally false assumptions on its meaning. Overused (and false) rhetoric includes:

At the end, they transform into the same breed of religious zealots that they hate so much, preaching their intolerance to everybody they meet. Narf.