Usually it's a case of a well thought out decent post, but then you scroll down to comments and it's "men are trash" and etc, so you end up with a bunch of fighting, which detracts from the original point.
Prolly would be better if "comments on this are disabled" was more common practice.
Or if administrative systems actually punished people heavily for saying stuff like "(any group of people) are trash"
If the comments are threaded (like they are here), I don't get why any point can be considered to derail conversations. That's just one branch. If you don't care to discuss that branch, just scroll past or minimize it and find another branch or start your own. They can all be discussed in parallel.