Let's face it; some of the kings of the Old Testament were just as lecherous, greedy, and nasty as Mohammed. That's simply the nature of the Middle East.
Second, religious profession based on "Right or wrong, I'll sign onto anything if it's to my own personal advantage" is spiritually depraved--- wouldn't you agree?
Third, there is a big difference between Biblical history and Biblical Law. Biblical history is full of homiciders, woman-abusers, looter-heroes, Israelite and Canaanite gang-bangers, long lines of apostate swindler-kings (check out Jesus' genealogy starting at Matthew 1:1)--- with glimemrs of "there is something better" "something better is coming" --- and then Jesus, symbolically framed between Elijah and Moses at Tabor as perfect fulfillment of the Law and the Prophets.
While you're scoping the Genealogy at Matthew 1, you might also want to check out the Six Antitheses at Matthew 5:21-48.
This is not OT patriarchal desert-rat proto-Mohammadism. This is the Good Stuff.