George Carlin was not himself an atheist--he took the theist view that atheism is just another belief system. That is not to say, however, that he was any friend of the church. He saw in the institution of religion all the human follies and ridiculousness that has led many an atheist to the realization that religion is anything but divine. (Though in Carlin's case, it made for some divine comedy.) George Carlin made his career by taking a look at all that was taboo in society--like criticizing religion--and then skewering that taboo. The man was a meat-eater, and his diet consisted of society's Sacred Cows.
RIP, Carlin. You will be missed.