I think there is, yeah. Obviously it can’t be policed or a hard limit set, but from a reading-the-thread perspective it’s quite dull to wade through pages all responding to the same thing in the same way, particularly if there’s a long time between those responses so it’s not a case of simultaneously posting but instead, everyone wants a go; similarly if it’s not a factual error thing but simply a “lots of people don’t agree” it’s unnecessary to have a pile-on. (I don’t enjoy seeing pile-ons in AIBU, either!)
But saying that you find the discussion 'dull' isn't the same as it being a 'pile on'.
And if the poster in question digs their heels in and continues to defend their factual inaccuracy, despite evidence to the contrary having been posted, as happened in this case, then of course posters are going to continue to point out the error. It's a public discussion board, and a pretty tame one in the scheme of things. If you say something which is just plain wrong and chose to insist upon it, you don't get to plead 'bullying' when this is pointed out.
And to be honest, it's not up to you to say what's 'unnecessary' or not. Some of us might find repeated sneering at other posters 'unnecessary'.
And I don’t think it’s entirely a case of developing a thicker skin or more resilience; as a pp pointed out, maybe multiple posters have brought up the sense of being “hounded” because this board can sometimes go that way, more so than AIBU.
There's only a fairly small number of 'core' posters here compared to AIBU, although the recent spate of name changing has muddied the waters somewhat. So perhaps people take things more 'personally.'
(For the avoidance of doubt, I don’t think this thread is that, and I think the tone of this discussion has been robust but civilised.)
Good to get your stamp of approval.