Escaping Original Sin?

I've been following this thread over on Et tu, Jen with a certain amount of interest, in part because it involves a fascinating mix of people. One comment from a Catholic-turned-atheist struck me as worthy of brief discussion, simply because it seemed so out of left field:

It wasn't until I finally started allowing myself to buy reality that I started to feel better. Today, I'm an atheist and proud of it. Damn, it's great to be free of the shackles of "original sin"!

Now, I have a skeptical enough turn of mind to have a certain degree of sympathy for certain brands of agnosticism, if not atheism, but this I have trouble wrapping my mind around. If there's one thing that seems clear about humanity, it's that our instinct tend towards evil awfully easily. Even if one discards the idea of 'evil' in a moral sense, humans fall to self destructive impulse (good neither for themselves nor for society) terribly easily. With the higher cognition with makes us capable of living in complex, tool using societies comes an oft-misguided willfullness. (You don't see ants or gophers indulging in self destructive and anti-social tendencies to the extent that humans do, though our primate relatives can give us a pretty good run for our money.)

So how exactly could discarding belief in God mean escaping original sin? Original sin is essentially the idea that as a human tribe we bear a (self inflicted) warped will, one easily led astray from 'the good' to the persuit of that which seems good, but is indeed far from it. If one believes in the Christian God, that means that we are born at a distance from God, wandering in our own created wilderness, tending to follow our own compass rather than God's. If one does not believe in that conception of God, it hardly changes this tendency in humanity. It just leaves it unexplained and with no where to go back to from that state of moral wandering.