Semantics! Regardless of one's personal knowledge, if an omniscient being has already foreseen the results of everything, then anything you do will only lead to those results. While you may perceive it as free will, from the perspective of such a being it's predestined.
Yes, theologians have been wrestling with this problem for centuries, with little or no success. Evil comes from Satan, they say. But God created Satan, and that omniscient God knew that Satan would bring evil to the world, so God knowingly created evil.As for the existance of Evil geting in the way of omnibenevolance; I shall refer you to the philosopher St Augustine who wrote so much about it in his work "The City of God".
The God in this quote is, of course, the traditional Judeo/Christian/Islamic God as defined in the Old Testament. While this does not say that a god or gods cannot exist, it does refute the existence of God as we've been taught to understand him.From "God: The Failed Hypothesis", by Victor J. Stenger:
"The problem of evil can be formally stated as follows:
1. If God exists, then the attributes of God are consistent with the existence of evil.
2. The attributes of God are not consistent with the existence of evil.
3. Therefore, God does not and cannot exist.