The minority are concerned because the US government has done unethical and malicious medical stuff to minorities, which makes some level of hesitancy for those groups understandable. Not the cod oil instead of vaccines bullshit white middle class and up promote, that is pure snake oil propaganda.
They weren't intentionally infected, they were just deliberately not given the cure. It doesn't make a difference at the end of the day, but it is important to distinguish because that is probably part of how those involved in the study justified their actions.
E.g.,
"I didn't give them the disease, so I'm not responsible for what happens to them"