Here's an interesting conjecture. Moses is sometimes depicted with horns; here's Michelangelo:
I agree with Freud that it looks like Moses was a high-ranking Egyptian official who believed in the monotheism espoused by Ikhnaton. He is said to have been versed in all the wisdom of Egypt, which like all primitive religions, was basically black magic, trying to get the invisible world to do your bidding. Whoever he was, Moses had a strong motivation; maybe he was a high-ranking demon who realized the truth of things and wanted to set things straight. That's how I see myself, anyway.