I think the argument is that the further left you go, the more likely you are to explicitly describe yourself as an anti-fascist and make a big deal about your opposition to fascism, as opposed to just quietly disliking fascism like most of us do and not feeling the need to announce it.

Like all sane people I oppose fascism, but I don't put "anti-fascist" in my Twitter bio, wear antifa t-shirts, or run around loudly telling everybody about how much I hate fascists, because why should I need to? Of course I'm an anti-fascist, who the hell isn't? It feels as unnecessary as having to tell people that I'm "anti-genocide" or "anti-pedophilia".

It's also true that communist regimes have always used "anti-fascism" as an excuse for their atrocities, just like fascist regimes have used "anti-communism" to justify their atrocities. The original Antifa was an offshoot of the German Communist Party, and (as GP pointed out) the Berlin Wall was officially called the "Anti-Fascist Protection Rampart". That doesn't mean that all anti-fascists are communists, but history is what it is.

Don't take any of this as my denying that there are still fascistic forces in our world that should be opposed. If "anti-fascism" is an important part of your identity and you feel the need to tell the world about it, good for you, I'm not going to stop you, but personally I don't see the point.

It's the same spiel the communists did with calling themselves democracies.

Democracies usually don't call themselves The Democratic Republic Of X. Communist dictatorships do that. Democracies don't build a border wall and call it an anti-fascist protection-wall, communist dictatorships do that.

When someone loudly and repeatedly exclaims how holy and pure they are, my alarms are going off. Yours aren't?