They just need a quick, easy way to dismiss people without actually engaging their argument. I get hit with something similar sometimes. ".ml, argument invalid." because they don't want to admit they're supporting genocide.
i think in this specific instance its serving the same purpose of demonizing our ideas by using a popular hated strawman. which was jews at that time, but is russia now.
in general this is one the final purposes of these -isms and -phobias they keep pushing constantly.
It's also just completely inane. Okay let's say I was a russian asset, does that change the fact that Joe Biden has deported more people? It's just a thought killer meant to ignore any criticism.