I will just note for the record that having an "argument corner" is a terrible idea, because it fosters exactly this type of attitude: the impulse to call out foes to the dueling ground and appeal to the implied audience rather than dealing with conflict like a mature adult. Individuals with such tendencies are emboldened to do things like come back and try to rally the troops as in this case, and people who aren't inclined that way will feel either that they cannot call out bad behavior without recourse to the Public Shouting Match or will naturally fall into one camp or the other and become the baying crowd that feeds these antisocial dramamongers.
Both options - letting inappropriate conduct fester or creating an ersatz gladiatorial culture - are future problem points for any community. I would strongly recommend removing the argument channel and instead focusing on behavioral expectations via standard moderation practices. You don't want a community where the loudest and most aggressive or most skillfully manipulative are encouraged to ply their trades for clout.