I wish you hadn't added that bit, it will give someone the opportunity to tell us that they've got a black mate and he doesn't find it offensive so that's case closed.
I'm not sure anyone has ever worn fancy dress to 'look up' to someone? He's basically saying that the only thing that stands out about Bony is that he's black (and that he plays for Swansea). Why not wear a massive strap on to throw a stereotype in to the mix.
So why did he go as Wilfred Bony and not Leon Britten, Jonjo Shelvey, Angel Rangel or Gylfi Sigurosson? Because Wilfred Bony is black and that means he gets to black up and it's oh so funny. That's why some people might think that it's not a terribly good idea. Added to that, the ONLY likeness...