The answer to the charge of “racism” could simply be “communist” in return. Let them respond every time to that charge.
Another possibility would be “societal rapist”.
It has to be personal, loud, and take them off their game.
Good idea. Just start reading from the cpusa goals and ask them what they disagree with. If they fall into the “communism isn’t so bad” script, ask them why so many of the the commies own countrymen had to die to put it in place.