If a famous person uses that fame to speak out on politics then they deserve political scrutiny..thats only fair.
We have a rule at work that we never discuss sex, religion or politics with customers...and I'd be very upset if my political opinions effected my job.
But if chose to start using my job to promote my politics then it would be fair to consider that as part of my job performance.
My parents taught me the same thing and called it "polite conversation".