I am able to accept someone as The Bad Guy without knowing the least little thing about their sex life. Do you know why this is? It's because a) the world is full of evil that can be done without having the least thing to do directly with sex, and b) I am aware that many really good people are into things I am not into, sexually as well as nonsexually, and that is--within reasonable parameters including but not limited to consent--quite all right with me. Sure, some villains Really Must have their villainy interwoven with their sexuality. It does not have to be the default. I promise it does not. And frankly it gets boring. "I'm not really sure this is my business," may be the Minnesotan polite translation of, "I don't care what happens to these people!" It still serves the same purpose: not reading your book any more, okay, buh-bye.
See also: cruelty to animals. It is not strictly obligatory in a villain. What ever happened to the cat-stroking villains of yore? These days they would be forced to kick the cat just to demonstrate that's the kind of person they are. Memo: humans are animals. Being nasty to humans counts.
I'm going to go read W. H. Auden. W. H. Auden never does this to me.