The Problem of Evil

With the tsunami catastrophe and other in the news suffering, the issue of evil and the existence of God is front and center. Here is a post on infidels.org message board from an atheist:

Here’s my own proof of the nonexistence of God. I maintain that not only does God not exist, he cannot conceivably exist.When I mention the word God (uppercase G), I’m referring to the god that most people in occidental society believe in which comprises the gods Yahweh, Jesus, Allah, and even the Hindu god, Brahma. Seeing that this God is said to be both omnipotent and omnibenevolent, then he has the power to wipe away all evil and suffering. Moreover, his omnibenevolence would move him, out of compassion and love, to end all suffering (or better yet, not allow suffering to ever start). Since the world is full of cruelty and suffering, the belief in this deity cannot be logically or factually reconciled with the state of the world. Ergo, God cannot exist.

His argument is standard fare and nothing new. The problem of evil, as far as I'm aware of, is the only positive argument from the atheist for the non-existence of God. There are several variations, but it boils down to the same issue: If God exist and He is all-good, all-powerful, and all knowing, then He would stop suffering and evil. Evil and suffering exist, therefore God does not exist.

I'm not going to deal with the nuts and bolts of the above argument, but it seems to me that the post above assumes a few things. He implicitly assumes a standard of good and evil, right and wrong to judge God. What is that based on? Also, he doesn't mention omniscences as a characteristic of God. Why? Is it possible that he knows his argument is weakened by the fact if God knows all, He ultimately knows the reason for suffering and cruelty?

God's existence due to the presence of suffering and cruelty is not so easily dismissed nor is it easily answered. So far theist and in particular Christians have the most cogent arguments that I know of, but I am a little biased.