No action taken.
Look, the number of "ballista fights" that keep popping up is rather ridiculous, it's just a case of acting like adults to avoid it. If someone is using it, then leave them to it, if you want to use it, just ask, if you're sworn at or something then just leave it be, the bloke is a twat, simple as that.
By all means report attackers but from the apology I assume Ronin knows he did wrong and will act differently in this situation if it presents itself again!