The NYC Rent Guidelines Board is already tasked with keeping rents lower for rent stabilized tenants, except with long term sustainability in mind. A pledge to put your thumb on the scale to freeze rent for 4 years is a clear sign of prioritizing short term political optics. The clever part about this is even if tenants suffer, he can just blame any negative effects on "greedy landlords."
It is worse for anybody looking for an appartment. Of course the person already living in one isn't worse off, but that has never been the issue that rent control creates. It disincentivises repairs and new constructions.
I think the core of the critique against rent control is that it mostly is a wealth transfer to the already wealthy, and that doesn't seem sensible. Or very leftist.