I recently watched a short film on YouTube that showed a fragment of a movie or series about a family of two or three white people who had a dark-skinned son, who traveled back in time to the 1960s or 1970s, or much earlier, when racism was common. They were walking through a park, and suddenly a man(B) appeared and asked if the boy was their employee. The travelers replied that he was their son. The man(B) became upset, and I thought he was looking for a fight.

EDIT: I don't know why the comments were deleted.

I really didn't want to promote hate speech or anything like that. I was just looking for this series/movie.

Thanks to bulfin2101

It is indeed the Doctor Who episode. Rosa