I don't think it makes you a "bad seed" at all, but I can understand that feeling. You're getting help for it and not acting on the thoughts, right? We can't control our thoughts, just our actions.

As for it having to come from somewhere, I don't know. I mean, some people have seemingly random phobias. And even if it did, it didn't necessarily stem from abuse. For example, it could be from something you read at a young age or overheard or accidentally saw on TV but don't consciously remember.
I say this as someone whose ex-T suspected something similar in my past, but I have no memories of it either. (She didn't push much for it though.)