Explain the line "Many of the White peoples stopped their cars, and took in the black people to help them on their journey to Alexandra

On the way back to Johannesburg, Msimangu and Kumalo watch people riding bicycles and walking because they cannot take the bus. They watch a car driven by a white man that the police stop because he is carrying black passengers. The white man confronts the police and dares them to take him to court. Kumalo smiles at this, for such an act is not lightly done, but Msimangu claims that this kindness "beats" him.