To me, this is a big part of why leaning too hard on the "social democracy is fascism" line is a bad idea.

1. It was a highly specific comment to begin with
2. It was abandoned in favor of anti-fascist cooperation within a decade
3. Today, it makes you sound like a crank unless your audience knows a decent amount of early Soviet history and agrees with you already
4. Even among people who kind of know what you're getting at, it's more divisive than useful

If you want to criticize a group for bad stances on imperialism, or a government for a bad imperialist record, just do that.