GOP gubernatorial candidate Bruce Blakeman had harsh words for Mayor Zohran Mamdani as he headlined a Sunday rally against antisemitism in Queens that was attended by about 150 people. “One of his first acts as mayor was to change the definition of antisemitism. We don’t have enough problems in the city? That was the first thing he had to do?” Blakeman told The Post when asked about Mamdani’s handling of simmering tensions in the Big Apple, including a rowdy antisemitic protest outside Park East Synagogue last week. Nassau County Executive and NY gubernatorial hopeful Bruce Blakeman slammed Mayor Zohran Mamdani as “antisemetic” and “un-American” as he headlined a rally in Queens Sunday. Kevin C. Downs for NY Post “He’s got a dark heart. He’s un-American and he’s antisemetic. And he’s got to change or otherwise this city will rise up against him because this is a city of good people,” the Nassau County executive fumed. “This is a city of every race, religion, ethnic group.…