By far the biggest destroyer of religion is monotheism, which has extinguished countless faiths throughout Europe, Asia, Africa, Oceania and the Americas -- in fact, on every continent on earth. Monotheists have attacked religion verbally with critique; socially through persecution, slavery and forced conversion; and militarily with genocide.
Some atheists also attack religion -- verbally.
But not all do.
Everyone has their own thoughts but for me, what I think is that Atheist is when you don't believe that there will be a religion and not necessarily means they're against it. But for anti religion, they don't support the religion and are against it. So there is a different meaning for these two words.
I am an atheist, and i am not against religion. I think that some people can go a little overboard with their religion, but overall would never say that I am against religion. Most of my friends are religious and we get along great. I would however say that I am against people using religion to infringe on people's rights.