I guess that's a little dirrent than the large ammount of black men who are affraid of your dog...
lol jk jk.
Yeah associating him with the dog getting treats is going to be the only way.
When he comes over, give the dog a treat. When he's there, have him give the dog treats. eventually black men will = getting treats.
You actually have it easy compared to my parents dog who had no socialization with anyone other than white people, and take it out aggresivly towards anyone of a darker persuation. I've met plenty of dogs who are like that too.