Do sports stars have the right to free speech?

French football superstar Kylian Mbappe recently landed in trouble over a meme. Discussing an image that apparently superimposed his face on Mao Zedong’s, he referred to the late Chinese leader as someone he thought was a dictator, without naming Mao.

The offhand remark became an international controversy. Chinese sponsors withdrew their support. State television suspended La Liga broadcasts. Ap...