Can I scream at a homeless guy to leave me alone?
Why would you do that? What did he do to make you scream at him?
He looked at me in a weird way so I got angry at him.
That was a mean thing for you to do. It is always unkind to yell at strangers. He might not have been looking at you in the first place, so its wrong to jump to conclusions.
Then he was supposed to look the other way until I was gone.
That might be too much to ask for. You shouldn't yell at somebody for looking at you. And if you yell at strangers people will think you are crazy.