I agree with the OP. It can really nasty here. It is disingenuous and faux-naive to say otherwise.
Some posters just like to have a go, others have had an empthy bypass, others enjoy the sensations of superiority and/or self-righteous indignation.
Often the tone of the OP dicates if they get a kicking or not.
Here's an example. There were two different threads on the same matter: doing a job, with no actual work to do (zombie jobs, I guess).
The first one explained that they found it soul destroying and asked if others had been in the situation. All the replies were decent (all agreed that it was indeed horrible).
The second one complained that they were misled in the job interview and that they hated it, were isolated and had personal difficulties on top. The tone was much more "moaning".
The replies became a bit of pile on. The gist of the replies were "because I have a terribly stressful job, you should be grateful to be able to write a book/learn a language/do fitness classes on company time and money." About 4 pages of it!
There was a few months between these threads, iirc. Of course, there have been others but that is the clearest contrast I can think of.
My personal bugbear is in relationships: "get some self esteem", when someone's partner has turned out to be a dick. You lay yourself bare, are emotionally vulnerable and some random on the internet makes you feel even shitter because you lack of confidence. Very helpful.