I could be wrong but it seems to me, this is a bigger deal to "virtue signaling" white people who care more about bringing a political candidate down, than they do about offending people of color. They like to sound as if their motives are more noble than they are.
From what the people of color I know say, they don't necessarily like it but aren't all that worried about it especially given the context of someone dressing up in a costume that was made more authentic by having the coloring of a person who they are emulating. Similar to a black woman wearing a blond wig if they were dressed as Marylin Monroe. Or when a black person marches in the St' Patrick Day's parade wearing a red wig and a Leprechaun costume( I've seen this). If the costume wearer was doing it to promote some negative stereotype or they were making a mockery of a racial group, then they'd have a problem with it.