I'm mad at my boyfriend when he said all girls who game are bad
Why did him saying this make you mad?
I'm a girl and I like to game therefore I'm a bad girl
Being a girl who likes to play games doesn't make you bad. It sounds like your boyfriend is making bad stereotypes about your gender, and you should probably tell him how this makes you feel if you want to keep your relationship.
You are right. He shouldn't be saying those things.
Do you know why he would think those things? Seems pretty illogical to have those thoughts today.