Mayor Zohran Mamdani speaks in the Bronx about his new program, Organize NYC. Matthew McDermott for NY Post What a sick joke: Mayor Zohran Mamdani is burning city cash to stage angry crowds to demand the Rent Guidelines Board — already controlled by his appointees! — make good on his rent-freeze campaign promise. In political circles, “astroturf” is the term for fake “grassroots” activism-for-hire; this is just taxpayer-funded astroturf. The mayor actually boasts of how his Organize NYC will pay professional hacks to recruit people to put on this pointless show as the RGB “considers” whether to freeze regulated rents for 1 million city apartments. He’s basically spending public funds (amid what he insists is a budget crisis!) on recruiting his own Mao-style Red Guards to bully any dissenters into line.…