Start talking about politics again. If it's impolite to talk about politics, only the impolite will be the one's talking. Discuss, respectfully, what your thoughts an opinions are. Challenge ridiculous ideas. Don't just roll your eyes and walk away. Engage (as much as is reasonable, don't start fights)and be prepared with facts.
It's not easy. I don't follow this advice all the time. Pick your battles when it won't affect your career. But be prepared to have the conversation when it comes up.
I don't disagree with you, but that's not what I'm talking about. I'm saying in normal civilian life, talking with friends and family, it has long been considered taboo to discuss politics at all. Treating friends and family with respect is just an important part of fostering healthy relationships. Public officials, pundits, and celebrities don't require the same level of civility, because I don't expect to have a personal relationship with those people.