A black man working at a mall as a Santa is by no means a bad practice.
Hiring a black man to be Santa at a mall just because he's black and you need "diversity," is, in my opinion, a bad practice. Not saying that this is what happened here, but, I wouldn't agree with it if they only did it because they needed a black person in there.
I hope he enjoys working there and I hope he encounters no problems while he does.