The note was a dick move, but why is bro agitating them? Ok, they don't want you to park there, that's not their call and he can choose to park there again if he wants, but HE'S creating the freakout here.
I don't agree, I think he was checking for racism so his buddy knew. They were definitely racist, they said they've never done this before, he doesn't live in that neighborhood, etc., etc.
Maybe they are maybe they aren't. He walked up to their house to confront them about the note. He needs nothing from them. They didn't block him from leaving, they didn't take anything, but he's still standing outside their house yelling at them. His goal was to create a scene for views.