Probably an avalanche effect. It's seen as socially impermissible to talk badly about your specialty among your colleagues for a number of reasons. But once a person who is respected does it, others feel comfortable following. The more who follow, the easier it is.
Personally watching the forum I've found it rather nuanced. I followed sunlioness's posts with great interest, but I found her to be very balanced in her assessment of everything. I was even surprised to read someone say they enjoyed doing college mental health—I was sure that would get jeers. In general it seems like the people on this board enjoy the actual work with their patients, with the exception of people they haven't been trained to help, can't help, don't have time to help, or don't believe have problems that can be helped by psychiatry. I get the sense that when they think a person is appropriate for the psychiatric help they can provide, they seem to enjoy that.
Although, there must be some of a challenge for it to be rewarding. I wonder where that rub is. I remember the most excited customer I ever had working in customer service was a case where I had a woman reset her iPhone (holding the sleep/wake button and home button at the same time). I got such undeserved praise for something most people already know how to do. And then there were the cases where you had an angerball that you couldn't help (fix the person, then fix the problem was our motto). But the fun ones were when you figure something out that you didn't already know, or made some weird connection. Like isolating a hardware vs software problem by walking someone with an erratic trackpad through the accessibility options to turn on mousekeys, and when this works and stops the cursor from behaving crazily being able to positively identify the problem as hardware based. That's fun. Because they don't train you to do that. And it's also the cases where the customer doesn't necessarily realize it was rewarding for you. I would imagine it's the same with psychiatry.