Actually, the title of this post is deceiving, because I have a personal short answer: NONE! However, as with anything else that would have my name attached, it depends on where the artist, athlete, etc. is making the political statements. Here's what I mean...
An example in art is the work of Diego Rivera. It's often overtly political. The message of workers' struggles and rights (socialism vs. capitalism) is clear. In music, the protest songs of the 1960's and 1970's contained lyrics against war, and that sentiment was rarely hidden in poetic symbolism. George Orwell's novels ANIMAL FARM and 1984 were political warnings about how the people can be easily manipulated to become monsters in unwitting support of a brutal political regime.
I have nothing against any of the above examples. If the consumers of art, music, or literature don't like the general message, the simple solution is not to buy or commission the work.
I do have a slight problem, though, when the entertainer gets specific in the work, and a much more major problem when the entertainer attempts to use his or her fame/popularity as a platform to persuade followers and fans for or against an issue or a candidate. I will protect myself by not naming names here, but you may get an idea of to whom I'm referring in these cases. I was a great fan of a super-best-selling author...until he supported one presidential candidate and attacked another. I loved the music of a rock superstar...until he did likewise. I adored the work of an acclaimed actress...until she took political sides. Though I'm not a fan of professional sports, the athletes of the NFL and NBA have become political cheerleaders. I would prefer that all these entertainers would keep those opinions to themselves and their small circles, like the rest of us do. You risk losing fans and followers otherwise. So shut up and act, play your music, write your novels, or dribble and shoot.
I bring this up because in my work-in-progress I'm at least borderline political, and in a nonfiction work that I'm outlining, there is no border: I'm outright political with my opinion. I would love to become a bigger name, but I hope never to use that name as a platform in support of a political movement, and certainly never for a politician. Those people can't relate to what the rest of us real folks truly need, so why should we throw them our support?
Today's rant over...Now on to watching the Soccer World Cup in hopes that Poland can finish above its former fascist occupier, Germany.