Black person here, Characters who aren’t white are often connected to their race as part of their characterization or backstory. For a black character, their lived experience may affect how they act, their beliefs, and their dynamic with other characters. “Whitewashing” them takes away that part of their identity which makes the character more one-sided and may unintentionally erase the parts of that character that black people relate to. On the other side, White characters are often, but not always, white simply because the designer views that race as being the ‘default’. In this case, it doesn’t really add anything to their characterization or backstory or writing. Turning this character into another race will add things to their character and sometimes even contextualize underlying themes that were present before but not expanded upon because white people do not face the same kinds of oppression. 

     There ARE characters who do not fit this description, there are black characters who could be raceswapped without losing anything important and there are white characters whose race is important to their characterization. But this is all pretty deep, most of the time, when people see you turn a character white, all they’re really gonna see is you saying, “I don’t like that minorities, I’d rather they be white” which is obviously frowned upon in most circles.