A Kafkatrap is defined as using denial as evidence of guilt, it was coined by Eric S. Raymond in 2010 in reference to the book Der Proceß by the term's namesake Bohemian author Franz Kafka.
The regressive left frequently exhibit this behavior by slandering people as racist/sexist/whatever for violating their extremist ideology, with the only legitimate defense to these allegations being to out the source as extremist with the origins of the allegations being the accusers ideology and definitions rather than objective facts, which is something that would not be accepted by the regressive left as they consider all criticism of their deluded extremist ideology illegitimate and thus rooted in whatever is relevant in their retarded arguments.
As their behavior often fits the definition of a serial harasser, the only way to make the shitheads stop is to call them out publicly and spread the word about their terrorist ideology to everyone so that they can avoid and ignore them for their shitty behavior. I also recommend any site that's hostile to the regressive left take measures to fight the freaks by banning them on sight for harassment and stalking, hate speech, and the promotion of terrorist ideologies and conspiracy theories.
One of the things I have done previously on a Discord I help moderate (yes, yes I know - and no, it's not a Discord you will have heard of) if, when accusations like this are thrown around, follow it up. If someone's just shouting "Racism!" because they got banned for being an asshat, pursue it. It's a very serious concern to raise, I need all of the information you have to get to the bottom of this matter.
It does not normally take long to get down to brass tacks; the person's asserting racism due to ideology rather than any factual basis.