New York Police

My experience with New York Police over the years has, although not confrontational, not been good. When I have seen any of their actions my impression has been that New York Police are arrogant and prone to unnecessary violence. That is safe enough when the police are acting in a ghetto: they can get away with arrogance and violence because their superiors will back up anything they do to break the law themselves. If the victim of their bad behavior is poor and in a minority the odds are that they can't take their oppressors to court.

But it is bad policy to assign stupid, and especially stupid, racist and arrogant officers to duty guarding posts where there are diplomatic personnel around. In this particular case if the policeman didn't recognise Ambassador Gonsalves as having diplomatic immunity, perhaps because it was his first day on that post, he should have known that there were diplomats all over the premises and if he didn't recognize a particular diplomat he should have explained that to Ambassador Gonsalves who would have waited politely while the NYPD found someone who knew what he was doing.
And if the policeman couldn't bring himself to be polite to a person with a dark complexion he certainly should not be on duty anywhere near the UN. I'd suggest he be reassigned to Staten Island.

I would also suggest that the policeman's superiors, who didn't train him properly, and their superiors, who evidently weren't aware that putting an arrogant, racist policeman in a sensitive position wasn't a good idea, at the very least undergo some training in respect and common politeness before they are assigned anywhere near anyplace where they might encounter diplomats.