I think you'll seldom find an atheist who does not believe his beliefs are right and all others are wrong, hence the comment, the veracity of which is quite tenable.
Absolutly, I believe that Christianity is just as delusional, just as much a fairy tale, as Islam, or Judaism, or Hinduism, or any of the other tribal creation myths we see floating around today. The difference is, I don't condemn those who embrace religeon as being "morally repugnant." I don't assume that, simply by virtue of going to a certain church, a person is doomed to an eternity in hell. I don't attempt to preach to the masses that they are horribly wrong, and shall suffer for their sins. I let people do what they please.
I find the Christian beliefs wrong not because they are different from my own, but because of what they are. The Bible asks us to condemn gays, "Heathens," women. The Old Testament is a war story, about one group of fanatics trying to gain regional supremacy, using terror tactics and genocide. It isn't a story of love, or human decency- it is the chronical of a monsterous mythological figure, who incites his followers to cause pain and suffering. It is irrational, and disgusting.
That's the difference between the Atheist assertion that Christianity is wrong, and the Christian assertion that Atheism is wrong. Atheists have never lead crusades or started inquisitions, friend.