White people smell different than black people, who smell different than Asian people, who smell different than Hispanics, and so on. I think dogs simply pick up a scent they don't immediately recognize and freak out. I don't think dogs are racist, though that behavior can certainly be reinforced by their owners.

For the most part, growing up in a white neighborhood does explain it. More important than that is whether or not, and how often, your dog is in direct contact with people of different races.

As for correcting it, you need to make sure the dog understands the behavior isn't acceptable. I don't own a dog, so I won't comment on specific training methods, other than making sure any punishment is actually a punishment (for example, putting the dog outside when this happens can backfire if the dog likes running around outside).

Dogs are not PC, unfortunately. They need diversity training within the first 16 weeks to really understand that humans come in all shapes and sizes and colors and amounts of mobility. They also need to learn about different surfaces, breeds of dogs, species of animals, etc.

Dog trainers call this process Puppy Socialization. If you had an 8 week old puppy, the answer would be to avoid the problem and come to puppy class.

But you don't have a puppy, you have a dog. So your best bet is to get an experienced dog trainer/behaviorist to help your dog overcome his fear of what he sees as unusual.

Here's another process you can use: http://willmydoghateme.com/dog-training-behavior/training-tuesday-bat-boy

The idea is to help him learn that he's safe around them. Do NOT yell or 'correct' his growling. You'll just end up with a silent biter.

My dog has a similar problem. He growls at anyone who is slightly bum/sketchy-like, black, Hispanics and old folks. Luckily for me, it's only strangers and when he's on a leash. I've fixed it by giving him a tug and keeping him very close to me when we approach them. If he growls, then I make him look at me and I say, "no". Be stern and consistent with the training every time and it will improve. It takes time for me and I still have to be watchful of him.

I highly doubt that the dog is racist, or maybe it's just I can't see it. Does any of these "black people" tease or irritate the dog, and how old are they? I know that younger folks like to mess with the dog.

Where did you get this dog? Was he trained by a white supremisist?

(I had a neighborhood punk think it was great fun when we were young to grab ahold of his friends and shake around like we were struggling, while commanding his dog to "Sic 'em, killer... Sic em!"

He use to laugh and laugh as the dog would jump and bark in defense of him, despite the fact that the 'victim' wasn't doing anything agressive... just being set-up.

Oh yeah, It was lots of fun...until that time years later when the dog got off his leash, ran through a neighbor's yard, recognised a neighbor kid and went for his throat... Hilarious! The blood went flying... [We pushed for the dog to be put down as he attack without command and for no apparant reason...])