The historical context argument is a valid one, but this one isn't. Why do all of Donald Trump impersonators paint their faces orange? After all, wouldn't the fact that they are wearing his ridiculous hair and imitating his voice and gestures be enough to convincingly portray him? If a black guy (for some reason) wanted to dress up as Tom Hanks, don't you think he should be painting his face white? If I wanted to dress up as Denzel Washington, shouldn't I least make the effort to paint my face darker?
Donald Trump doesn't have orange skin. People making themselves look orange when dressing as Donald Trump are doing so because he makes himself look orange with whatever fake tan/make-up he wears in many of his public appearances. He, himself, makes a conscious choice to look that way. The same is not true for people of colour.
If a black person wanted to dress as Tom Hanks then they would likely choose one of his many famous characters and dress as them. For example, if they were to do Castaway they could wear some worn clothes, a fake wig and beard that makes their hair look unkempt, and carry a ball with a face drawn on it. If they wanted to do Forrest Gump, a pale suit, a checked shirt and a box of chocolates would do the trick.
Likewise, if a white person wanted do dress as Denzel Washington (and I'd question why), they could go as his character from Flight and dress as a pilot, but carry a bottle of booze disguised in a brown paper bag.
In either scenario there is no need for anyone to change the colour of their skin. When you are dressing up as someone else you are doing so because of who they are and what they've done.
The Harlem Globetrotters were basketball players known for being very entertaining basketball players so a costume should focus on basketball.
Donald Trump is a celebrity-turned-politician that is known for, among other things, his dodgy hair, his strange mannerisms, and wearing whatever it is he wears on his face that makes him look orange.
Tom Hanks and Denzel Washington are actors, known for acting, so it would make sense to choose an iconic role and go from there.