Is it bad that I slapped him?
What would make you want to slap him?
I don't know, but I want him to be punished for trying to cut me the way he did.
Using physical violence or engaging in domestic violence against your partner is never okay and should be put to a stop as soon as it's recognized. Find more constructive ways to get your point across to him.
I thought it would be funny to abuse him physically. I was joking, I can't be held accountable for my actions.
It's your decision you should be held accountable. You can't go around and slap and hit people without something happening back to you.