No offense but this is a horrible argument.
Example
The fact that some people call blacks 'stupid niggers' or Hispanics 'stupid spics/wetbacks' while others don't doesn't really help reach any conclusion on if those words are racist.
You don't need an unanimous decision to realize that something is wrong.
That and I always find it funny that by large minorities don't feel the need to paint their face white to imitate white artists/actors/characters and you pretty much always know who they're cosplaying/imitating. But for some strange reason there's an actual argument that many white people just have to paint their faces black lest you be confused on who they're imitating. No that means you're just doing a very shitty job at imitating said artist/character/actor(ess). If being black is the one shining definitive characteristic of said character then firstly, it's an absolute shit character, and secondly that character just isn't for you.
On the subject of imitation, someone link
cosplaying while black and I recognize every single character these girls and guys are cosplaying as and they didn't need to paint their faces yellow and tape their eyes back to achieve it.
So on the point of people 'needing' to paint their faces to be close to an artist as possible.
They don't. Your musical performance isn't going to be any better or worse because you painted your face black. They're musical artists, you imitate their onstage presence and you sing their song and anyone will know who that artist is. If people don't know what artist you are when you're on stage and you feel you need to paint your face black; then you're doing an absolute shit job and should quit.