The National Basketball Association scrambled late Sunday to contain an escalating crisis in China after a Houston Rockets executive’s tweets supporting pro-democracy protests in Hong Kong sparked an international furor.

The league’s carefully plotted strategic emphasis on China was jolted off course on Friday night when Rockets general manager Daryl Morey tweeted an image with the words “Fight for Freedom. Stand with Hong Kong,” in reference to the mass rallies against China’s authoritarian government on the streets of the...