A Disproof of God's Existence (1970) by Michael Martin

If God is omniscient,
then can He be absolutely moral?

This is another article from Infidels.org which supposedly disproves at least one conception of God by pointing out the irrationality of one of God's attributes.  The article is very short and you can read it here.

The article presents an argument that God's absolute morality precludes Him from knowing what certain experiences are like, such as feelings of lust or envy.

The argument claims:

1. If God exists, God has not had feelings of lust or envy.
2. If God exists, God exists as a being who knows at least everything man knows.
3. If God exists as a being who knows at least everything man knows, God knows lust and envy.
4. If God knows lust and envy, God has had the feelings of lust and envy.
5. God exists. (By hypothesis.)
6. God has had and has not had the feelings of lust and envy. (By (1) - (5).)
7. God does not exist. (By (5) & (6)  Q. E. D.)

In other words, God's morality either makes Him a being who cannot be omniscient, or cannot be absolutely moral. If one imagines a God who is both omniscient and omni-benevolent, then there conception of God is impossible.

There article, perhaps in the interest of fairness, lists a few common objections and then addresses them. Many of the objections don't really hold water, but here is one objection which is not brought up, and I don't think Martin would be able to address it. He even admits that his argument is geared more towards the "common view" of God and acknowledges that no single argument can refute every conception of God. My objection involves a very uncommon view of God.

This disproof by Martin is very similar to the argument presented in Omniscience and Learning by Ryan Stringer. Therefore, the answer is very similar, too. 

"As man is, God once was; as God is, man may become." - Lorenzo Snow

Therefore, premise (1) is false and Martin's argument is invalid.