I’m assuming you don’t immediately try to turn any criticism against an instance whose politics you agree with, back on the mainstream instance.
I think that many people reflexively speak out against perceived unfairness. Why should they stay silent when they see people from a problematic mainstream instance constantly complaining about other instances that they see nothing wrong with, the vast majority of the time without evidence, I might add? I mean, it adds up to endless whining, even in completely unrelated threads. I often see it go like this:
Person 1: “Hey, did you hear about this new scientific discovery? Pretty interesting, huh?”
Person 2 (very often from .world or piefed.social): “Well, just stay away from the DaMn tAnKiEs! They’re horrible!”
Person 1 (or Person 3): “Huh? I didn’t say anything about any tankies. Besides, .world or piefed has plenty of idiots too.”
I’ve rarely ever seen anyone grumble about .world in a completely unrelated thread without cause (i.e., in response to a .world person saying something stupid), but I see that all the time against mostly the socialist/communist instances with some spillover to the anarchist instances. After a while, people start to react automatically to any complaints about other instances.
But that’s appropriate in this thread, since it’s specifically about a person on lemmy.world complaining about lemmy.ml. The scenario I was describing was of someone chiming in about the “tankies” in a thread completely unrelated to Lemmy instances or politics, like gardening or movies. I feel like I see this all the freaking time, but I suppose I could be wrong. It’s always a possibility.