"Why do we seek moral absolutes?"

As an aside, this might actually be a question with which science can one day assist in a solution. Example: we're already starting to hook up believers and non-believers to MRIs to look at differences in brain function.

I suspect a number of factors, broken or non-functional logic circuitry, including willful ignorance, the desire to feign wisdom, fearfulness of the unknown, fearfulness of change, and so forth.

There is an utterly baseless opinion of certain moral absolutists that if person X does not accept absolute morality, that "anything goes" for that person X or that the person "has no basis" for morality or that "morality that isn't absolute isn't morality."

We are deluded into thinking the universe cares. They assert that if the universe doesn't care for us, we are not important. Our sense of self-worth is not important. It's strictly the worth given to us by some outside conviction that matters. It's a sort of psychological abuse. In the extreme, it can produce these sorts of effects:
http://www.youtube.com/watch?v=h_CfqqzFndk