I heard that when people laugh because someone gets hurt it's because of hormones being released in your body.
There's also another term for people laughing when someone gets hurt and it's called Incongruity.
You're not a bad person if you laugh when someone gets hurt and I wouldn't be mad if I fell and got hurt and you laughed because I too laugh at myself when I get hurt and even when someone else gets hurt.
I guess it's much better to laugh than feel sad and depressed that someone gets hurt.
laughing at funerals is also common for some people and you're not a bad person when you laugh at the funeral.