In the U.S. I first became aware of the term "Karen" after several high publicity cases of white women calling the police on black people just living their lives: barbecuing at Lake Merritt; selling water on the sidewalk (a kid); birdwatching in Central Park and asking a woman to leash her dog; entering his own apartment building. I think it's right to shame racist people for using their privilege to endanger others' lives. When someone calls the police about a Black person, they could end up killed. Something needs to stop the behavior, and shame on social media is one of very few tools available to the Black people who are targeted. It does feel vaguely sexist to me. I'm not aware of a corelative term for white men doing the same. But maybe that's because their behavior is more often fatal or violent so a silly name is not a big enough response. We don't call the killer of George Floyd a "Karen." We call him a murderer.