Thank you. I just discovered this phenomenon when my son (considered Black himself) brought home a big black bull terrier. He explained what you have said here - that her color meant she would be much less likely to be adopted than another color dog. Despite her reputation and size, Vida is the sweetest dog you could imagine. The only "danger" from her is that she is so excited to meet people she will jump on them and slobber all over.
The fear and discrimination you describe I have personally witnessed since. For example, near the beginning of the Pandemic my son and I took her to the beach. There was hardly anyone there at the time. Vida's delight was short-lived, though, as a lifeguard raced up in her vehicle to tell us that dogs are not allowed on the beach; she was "nice" enough to not give us a ticket if we left immediately. Since then, though, I have seen hundreds of dogs on the same beach, even different-colored bull terriers, parading right in front of the lifeguards without a word said. My son thinks this discrimination is at least partly due to his own blackness, but I haven't been brave enough to bring Vida myself to that beach.
Perhaps we should learn something from our dogs. They rely more on smell than sight. Something doesn't "smell" right with all this.