I think it's possible to be an ethical psychopath.

There's an interesting TED talk by a psychologist who didn't realise he was a psychopath until he mixed up his own brain scans with those of a psychopath he was studying.

He did have a history of bad behaviour in his past but it seems that he focused on trying to be ethical once he became a psychologist.

It would be difficult because you don't get the natural reward chemicals for doing good things, or the natural feeling of empathy to prevent you doing bad things, but I'm sure it's possible for some.

I also think that a lot of abusers don't have personality disorders.