Dogs obviously cannot be racist.
However they can be worried about and reactive over things they have not been well socialised to, people, other animals, things they have not made a positive association with.
Kicking off at seeing different coloured, shaped, sized people is no different to reacting to seeing a human growing out of a horse (horse and rider) or someone using a wheelchair (weirdly gliding along when seated humans normally stay still!) or any other novel thing.
Distance - find the distance at which the dog can see and NOT react.
Positive association (classical conditioning) - pair seeing the trigger with high value treats, until the dogs emotional response changes. This is not 'training' there is no need for the dog to behave, be good, sit, down, whatever, this is pure classical conditioning 'thing/person/event = reinforcer'.
Gradually reduce distance and add in other elements like the person talking to the dog, moving, standing up etc verrrrrrry gradually.
Do not:
Yell at the dog.
Use aversive devices like prong or shock collars.
Have the object of their fear lure them in with food (gets them too close then once the food is gone, they're in at the deep end without any distraction, a great way to get a bite!)
Flood the dog (have the person they're scared of move in for a week, or take them to a super busy place), this is likely to make matters worse, not better particularly as it can lead to the dog shutting down and NOT reacting which LOOKS like the dog is better... until that suppression fails.