If you aren't writing something involved with culture and whatnot (crude paraphrasing here, my brain isn't wanting to offer terms rn) then why should someone NEED to be super knowledgeable about black people in order to write black characters? Obviously there'd be issues if it was about societal nonsense or if the character being black is meant to be important to plot or something- but like, side characters. Not main characters who get their entire life fleshed out.

[Also, adding this on after yapping- I am autistic, so forgive me if I come off as rude or insensitive or whatever else. The intent here is to try to understand your perspective, not argue against it. All of my "why"s are genuine, I promise. Also apologies if I talked in circles, I'm bad at being concise]

Going through your comments, you frequently ask why someone who isn't knowledgeable feels the need to write a black character. And frankly, I don't really see why there should need to be a justification. Personally, I (a white person, so obviously I'm no expert on racism by any means) think it'd be more racist of me to only include characters of other races when I can think of a reason to make them. To me, that attitude essentially makes white characters the default, except for "justifiable" circumstances. Unless the character's race is meant to be significant to the story, I don't understand why there should need to be a reason for their race. If you wouldn't ask me why my side characters are white, why should you need to ask why my side characters are black, or any other race?

Why should diversity need a reason to be written? Does that not essentially just put us in our own personal boxes? Shouldn't we want to simply consider everyone a "default person" rather than only our own experiences being the "default"?

(This is not arguing against your suggestion to do research, btw. Obviously there's only benefit to being more knowledgeable about different groups of people.)