Like, half of america is obsessed with the Joker right now. And as for being obsessed with borderline insane characters...who isn't? they are everything we can't be, they are able to break out of social norms. It's like a fantasy thing. And it's totally normal and not insane at all.
I mean, come on. Have you ever spoken to any teenagers, ever? If you start actually going around beating the shit out of people who are committing crimes, and aren't a cop, then you can come back to the boards with your "problem". Until then, you're just a fanboy, like the rest of the internet.
Go hang out on 4chan's /b/ board for a bit and tell me if you think you're the crazy one out there. Should put things in perspective.
Actually, don't go there. If you're really that easily impressionable, you shouldn't be hanging out on /b/.