Definitely, and that is one of my main fears/critiques of this whole fediverse thing. Ideally there will be a system in place to help mitigate that, if there isn't already. Defederating is also effective.
I guess my point is that any instance (or website in general) that was not started with the inherent goal of being a fascist echo chamber should be completely intolerant of fascist/bigoted ideas. Especially the big ones, like lemmy.world and Kbin. And they should do everything within their power to not let those ideas exist. The paradox of tolerance and all that.
Some people are too far gone and will just run away into the shadows, sure. I'm more concerned about the "regular" people who are exposed to those ideas against their own will and get sucked into this cycle of hatred.