I'm confused as to what you're referring to, lemmygrad? Nah I'm pretty sure those are just tankies and tankies are as I understand it basically what rightwingers think everyone left of Ronald Reagan is. Like tankies aren't just commies, they're fucking stalinists.
I don't know if Lemmy has an equivalent, but in Kbin you can block a whole instance as a user. For example, I went to https://kbin.social/d/lemmygrad.ml and in the upper right corner in the "DOMAIN" box there's a standard block button. I expect it means I will not see any comments or posts that come from anyone on lemmygrad.ml.
The further increased customizability of kbin has been tugging at my curiosity for weeks, but I haven’t taken the dive yet. You might have finally convinced me.