If a person is going to be a cop then I want them to at least have some diversity so as to be able to handle a wider range of problems and interactions (and to fill spots otherwise used by racist assholes).
This country has horrific systemic racism, and that might very will have instigated this scenario.
On the other hand, if there's a guy prowling between the houses of my neighborhood, even if he's in uniform, I'm going to call the police to make sure it's legit, and I'm going to describe him as best I can, including skin color.
The police always tell the public that they should call authorities if they aren't sure about someone pulling you over or at the door. Until you do such things to be cautious, and suddenly you're the bad person for not immediately obeying. Double standard.
Honestly, I've called cops on cops before, no need for them to be black. One because they were an undercover cop who did not identify themselves adequately and acted suspiciously, second another (or maybe the same) undercover cop that was driving recklessly through the streets almost causing accidents without even a cop light/siren. I'd probably even call if they were in uniform and acted suspiciously enough so dispatch could double check. Cops are workers and they are human, they are not above you or illicit activities themselves, recordings have proved this. I would call, just not place the blame on them while just sticking to why the circumstances aroused concern.
And even generally, calling official numbers to confirm a situation is even something that is increasingly becoming necessary with the number of scams coming out. I realize racism was probably a factor here, specially if they are calling while cop cars are outside and there is clearly a crime scene being investigated, but seriously, don't think this means you have to think twice about reporting suspicious activity if they are cops.
I mean, being real, I'd be less worried if it was some random dude.
But, whoever called that in just saw some dude in dark clothing fucking around. Unless you get the right line of sight, you aren't going to be able to see the few shiny bits on the typical dark blue uniforms. Especially not with a flashlight bouncing around, while you're looking out a window carefully.
Frankly, if a cop isn't wearing something bright enough to be seen through a dirty window and it be obvious it's a cop, it's on them if someone sics an angry goat on them.
The caller recognized that he was wearing police clothing, how else would he identify that he's a cop other than his uniform? They saw a black man in police uniform and assumed he was pretending to be a cop.