I'm going to laugh at a joke where a women gets punched
Do you think it is funny for a women to be punched?
I'm laughing at the joke because it's stupid
Well as long as you're laughing at the joke, it's fine I guess.  You shouldn't laugh at other people actually getting punched though, that's wrong.
Alright, but I don't see a problem with a joke about people getting punched.
Yes, it's generally okay to laugh at jokes that are made in jest, as long as the joke teller doesn't actually intend for any harm to come.  Just be aware that some others might not find it funny, so it would be best not to pass the joke along indiscriminately.