Most scholars think that these stories were invented by his enemies to discredit him.
He's usually played by actors who specialize in gender ambiguity: Ralph Bates (The Caesars, 1968), John Hurt (in the tv adaption of Robert Graves' I Claudius, 1976), Malcolm McDowell (Caligula, 1979), John McEnery (A.D., 1985),
But the rapes and murders don't symbolize the depth of his decadence. What does? Crossdressing: he dons feminine attire to impersonate the Goddess Venus.
Apparently drag is the epitome of pure evil.