Mapimpi had Frans Steyn on his outside, but he backed himself for the line and scored.
Frans Steyn called for the ball, and his body language looked like he was frustrated that he did not get the pass to make the touchdown.
After the game, during celebrations, Twitter is showing Mapimpi turning, then walking in the opposite direction. There are claims that Frans Steyn waved him away, but I can't see that.
I don't see any race motivations. A professional sportsperson can be arrogant so there is going to be some conflict between players, does not mean race is of any relevance here.