This isn't specifically about a basketball league. This is a choice between believing in personal freedom of expression, versus allowing a repressive foreign government to censor people who are not their citizens, all in the name of profit.
Who upped the ante? One guy who tweeted something, or a government who blocked a whole industry? NBA isn't forcing anything. They would continue showing their programming in China if it were not blocked.
Well technically you don't have to choose a side you can choose to do nothing which is its own side in a way and has meaning and consequence to the general population. People know that rich and famous people, or people in power really have the most sway in matters. So we mere laypeople can decide that you either choose a side or you have chosen to side against us. If you were looking at a person who had the ability to help, but choose to do nothing can you not see how people can be upset with them? Again sure you can choose to do nothing but I won't like you, I might stop supporting you, or I may even work against you.