The internet is full of arseholes. That is because it removes the filter which in offline contexts would make people answerable for their behaviour.
It would be very surprising if every person emboldened by the www's anonymity conveniently congregated in one forum. You are going to find some of them everywhere.
I'm old enough to remember the old-school chat rooms. These attracted some seriously abusive, disturbed, fucked up people, to the extent that I'd use block features to avoid any interaction with certain names so that if they did something drastic to themselves then I wouldn't have it on my conscience. They'd wait years sometimes for someone to reveal just enough information to dox themselves, and would then be harassed relentlessly in their places of employment, as would their families. Some were members of very nasty organisations. And the people in there were there day and night (as were their sock puppets) every day: it was the same names every time you logged on.
In consequence of getting sucked into the rabbit hole of one or two of these rooms for a time, I'm now immune to the vast majority of the shit I witness online. You can believe me when I say that online discussion board style forums - even those with the kind of reputation X has or the Kiwi one - are incredibly tame and pedestrian by comparison. As for Mumsnet - that so-called nest of vipers who 'radicalise' people and shout 'LTB' - compared with instant chat rooms their users are like a bunch of fluffy bunnies.
On the whole it's no bad thing that those rooms - at least as far as I am aware - have mostly died out.