I want to spit in a douchebag's face
Why do you want to spit in his face?
He once spat in my face and it felt disgusting
As you know, being spat on is quite an insult. But, you aren't going to gain anything by stooping to his level and spitting on him. Use your words and maturity instead.
I don't care about being mature, I just want to spit on him.
What your friend did was disgusting, but that doesn't mean you have to do the same thing. It's just plain gross to spit on someone.