Four word to repeat, as often as needed, every time he opens his mouth.
Shut. The. Fuck. Up.
Seriously. Every goddamned time he starts running his mouth, tell him to shut the fuck up, then either leave the area or turn your back and ignore him.
People have no subtlety nowadays. If I were in the OP’s situation, I would be deliberately obtuse. Agree with everything he says, and expand it to conclude the exact opposite of his point. Eventually he’ll get too frustrated to talk to you.