Hard to tell for sure, but the first guess would be that he gets a thrill from upsetting you.
Most likely simply because he can get a reaction from you that way and at some level he fears/feels that he would not get your attention by more proper channels.
He is behind a driving whell, feeling powerful and protected. Sometimes that is enough to make people behave in inappropriate ways.
Unfortunately that is all too relatable.
I have little to offer in the way of advice, but it may be helpful to remind yourself that you do not owe him attention in any way, and that he is likely not in full awareness of his actions and their consequences.
Also, try not to appear vulnerable to him if you can help it.