I absolutely disagree that the onus is upon us to take it to PM simply because a poster cannot follow very simple instructions and do so themselves if they have questions- and letting others always get the last word in again undermines authority; everyone has a tendency to see them go against what a mod has says with no comeback. No, absolutely not.
As for 'degrading'- that's just pointless pride.
No, sorry, this needs to be absolutely understood and enforced. If a mod says finish, it is finished- no arguments, no comments, no last words, nothing. Zero tolerance on this is the only way to stop much greater abuse that comes later.
If the patterns of the past had shown this was not necessary, we would not do it. But the p;atterns of the past have instead shpown an enormous propensity for people to take advantage of even the slightest opening left by a mod. So this is the way it has to be. As Storm says- all too often, absolutely no respect is shown.
If I say "You can take it to PM if you have any questions; now go back on topic", it is absurd for a poster to keep arguing it and then complain if I pull him up on that. It was not ambiguous, it was perfectly clear, and it is entirely the poster's fault for going against that.
You listen to the mods. You talk over issues by PM. This aching desire to make things public is not something that is going to be tolerated, because it has absolutely no purpose whatsoever other than to attack the mods and derail threads in the process. Too many threads have been killed stone dead by that aggravating habit.
And the people that get bans on this are people whose in-thread arguing with the mods is part of a much borader patttern of abuse, attack and flaming. It's very rare for someone to be banneed for just that in isolation.
In fact, it is very easy to exaggerate thos issue greatly. Only a tiny handful of posters have been affected, and they have been extremely aggressive and disruptive.