Personally, I define tankies as the fucks who support the Russian invasion and deny Tiananmen Square. You can be communist without being a fascist bootlicker
Lots of things work like that. It’s called connotation (personal definition and significance), which does not require denotation (an actual definition)
Slur, “an insinuation or allegation about someone that is likely to insult them or damage their reputation.” So, yes. I’m not particularly worried about slurs against tankies, just like I don’t care about insulting or harming the reputation of nazis
ETA: pigs is a slur for cops, that’s a slur I don’t mind either