It's not the regular labor day BBQs they're interested in. It's being deployed specifically to monitor parties and parades connected to J'Ouvert and the West Indian Day parade. Every year there's a spike in violent crime related to these events and they're trying something new to hopefully keep things more peaceful.
These events are mostly attended by people of color so I doubt the NYPD is going to say they're specifically targeting these gatherings but they are.
Any sort of prison time would risk his neo Nazi army attempting monthly jailbreak attempts.