I'm upset with him when but I have no right to be. What should I do?
What got you upset about him in the first place?
I don't want to think about it anymore.
If he never did anything to you, then being mad at him is inconsiderate and rude. Apologize for prematurely jumping to conclusions and getting angry.
Fuck that, I'll write about him in my diary so I can feel better and vent.
Well you need to stop feeling angry towards someone who didn't do anything to harm you. You have to see how that isn't fair to him.