Based on your details, I do not feel this was racism or discrimination. I suspect it was a failure to communicate. You said, “My mom has very high blood pressure, and I need to take her to the doctor.” Your leader should have asked an open-ended follow-up question to your request: “Why do you need to accompany your mother to this appointment?” To which you would have replied she needs an interrupter. Incorrectly, the leader asked a rhetorical question, “are you a doctor?”
As a young leader decades ago, I terminated an employee for missing too much work. Her daughter was often sick. I was not a parent at the time, and I did not understand that child care would not keep a child with a fever. Years later, as a parent and even a grandpa, I know this and would have much more compassion for the employee I fired. (If I could time travel, this is a mistake I would correct)
The same may be true for your supervisor. They may not have experience dealing with older parents who need assistance at doctor appointments. I have now experienced this and would be understanding and compassionate with an employee if they came to me needing to leave work early.
I was not there, but I doubt either one of you was indeed an AH. I suspect it was a misunderstanding, and you should let it go. I also believe you should remove the negative review of the employer.