He sounds like a cunning sociopath. Watch out from them people
I would personally respond with a plethora of fancy words, simply to say eff you and you aren't the shit you wish you were. I would definitely keep him under watch, and when the legal (or not) opportunity provides, even teach him a little lesson if he steps too close. He sounds confused and deranged, if you're going to exhaust energy into him don't entertain this shit, teach him a nice lesson.