Maybe it wasn't so much that Orpheus was having sex with boys as that he had stopped having sex with women? Maybe it did have something to do with angering Dionysus. In any case, it wasn't because he was demeaning women. And Ovid was a Roman. I think the Roman attitude toward homosexuality may have been a bit more mixed than the Greek attitude.
Pentheus, king of Thebes, was torn to pieces by Maenads, including his own mother, for spying on their rites.
And Actaeon was turned into a stag and torn to pieces by his own dogs for spying on the goddess Artemis.
What
Laura said. It's whatever version of the myth you read is why he died. I wasn't so much alluding to the sexual nature of Orpheus' death as I was alluding to the death of a man surrounded by a very agitated mob of women. His was the most famous I could think of right off the bat.
In the plot of Euripides'
Bacchantes Pentheus was persecuting the followers of Dionysius, so the god appeared in his town in human disguise, allowed Pentheus to capture him, and after some dialogue, took him to watch the rites in secret, then gave Pentheus away after revealing his divinity and the maenads tore him to pieces.
I'm not sure if this was based on a true myth story or just something Euripides made up.
As for Artemis/Diana...well, never watch a goddess bathing. Even if they forgive you, they will still punish you.
