Anti-semites pretending to be Jewish to get away with anti-semetic/negative behaviors.

Has anybody else encountered anti-Semitic people who pretend to be Jewish to smear dirt on our name or spread conspiracy theories and get away with it? There is somebody in a discord server who I was beefing with for a while, who would do stuff like change their name to ‘wingo, king David’s chosen’ after a fight while also saying horrendous stuff like certain terror attacks against Jewish people being false flags. Or making fun of the Holocaust?

Or is this a particular case with a particularly mentally ill person and not some trend with anti-Semites?