I'm going to tell my friend that the girl he likes is an asshole
Why do you wanna say something like that to your friend?
I just want to piss him off so I can have fun
Don't play with people like that, man. Making someone think someone's something that they're not is uncool.
Calm down, dude. I don't have time to take care of other people's emotions.
You're damaging your relationships with people by spreading such false things. Nobody will trust you if you continue doing so. Get a hobby or something to have fun.