I hate to beat to death the topic of Moses' horns, but I couldn't resist sending you this quote from James Kugel's "The Bible As it Was":
[Jerome's] translation was apparently based on the apparent connection of the word "beam" with "horn" in Hebrew: not only did this make good philological sense, but horns elsewhere were sometimes an ornament in headgear and a sign of distinction. The implications of Jerome's translation were not witnessed at once, but starting in the late Middle Ages, Western sculptors and painters frequently represented Moses as having horns. (Kugel, p. 437)
My apologies if Kugel has already been cited in the discussion. He didn't seem to find anything objectionable in Moses' "horniness".
Kugel hasn't been cited. Larry Swain and David Nishimura (see the link above) have made it pretty clear that Christian anti-Semitism was not directed at Moses and the OT worthies in general, so I'm now convinced that Michelangelo was trying to reflect what he thought the Bible said about Moses and was not demonizing him, nor did he expect his patrons to take the horns as demonic.