At the same time that's one of the bad parts of anonymous discussion. You never know if someone's an expert or a random person guessing (on ELI5), engaging in good faith or purposely trolling, etc.
At least on Lemmy, defederating is also a way of banning all the instance's users from your communities. If you're constantly banning one instance's users and their admins seem fine with it, there's really no other way.
"You know what, let's just play and we'll figure it out as we go."