There's no arguing that manners were better when one man could ask another to "step outside", and when it was over it was over.
The point is that all this pent up aggression is going to come out one way or another, and channeling it into a controlled venue just might cut down on driveby shootings and related crap.
At the risk of being considered a radical, I'm not entirely sure duelling should be illegal. It is engaged in by "consenting adults" , right? It is a formal structure to allow a near-equal engagement between two men who have decided the world isn't big enough for them both, and that they're willing to risk death to settle the matter. Absent duelling, people in that extremity resort to outright murder. I'd rather be challenged to a formal duel than shot in the back one dark night.