I think batman was wrong, the joker was right, and realistically it does just take one bad day. Everyone having the capacity for horribleness doesn't really take away from the nobility of people escaping that horribleness, though, or "choosing" not to engage in it. If anything, I would think it'd make that decision more noble.

At the same time, where does that leave the joker? Does it matter whether or not he "chose" to be the joker, or if he was just predisposed to be that way? I dunno, I don't really think so. The core reality remains the same, or else there is no/little coherence to reality, and we live inside of a chaotic hellscape. Which I'm not, you know, fully prepared to deny, but more I think my denialism would probably come from the idea that I need to enforce my own coherence on reality, to simply believe in it regardless of the validity.

Somebody stop me if I sound like I've lost my mind and this is totally off-topic, though.