People have a right to ignore him, to walk away, to refuse to interact with him, to pretend he isn't there and so on. I would because he would drive me up the wall and get on my nerves and for my own sanity I would have to. If he wound me up I would probably be in some form of argument with him. I may say things in the heat of the moment etc.
If that was a child on a playground doing that to your child, then you would be moaning, demanding something be done, encouraging your child to stay away etc so I don't see why it's acceptable for an adult to conduct themselves that way. He was funny and entertaining to start with, but now for me he has gone above and beyond that level where it's uncomfortable to watch and irritating for me.
I agree it does look awful to watch, but he's also good at playing. Sometimes we need to think of the effect he's having on other peoples emotions and the impact he is having on the whole.
Him and Katie for me are a separate issue, they clash because they are similar.