There's an old internet saying: Don;t feed the trolls.
Meanwhile on another topic,
Yes. There is a twofold technique:
Never reply. Two reasons, one is Agent always replies to your reply. Two, there is some old internet saying that might apply here.
Report personal insults, off topic posts, baiting, or any other forum rules violations. If you scroll up and look at Agent's posts you might notice that part of their posts have magically disappeared.
Meanwhile, on another topic,
I don't know how or if the mods give penalties for frequent rules violations, but one can hope that if a poster accumulates enough violations they may decide to reform their antisocial practices or magically disappear as well.