Speaking from my own moral compass - I don't think there's a moral obligation to bring up politics with people I know with whom I disagree. They have their opinion, I have mine.
I think that's even true when a horrible ideology is gripping a nation. The Bolsheviks and Red Guards were not to be reasoned with by neighbors in their heyday. "The wise man sees trouble coming and hides himself."
I'm reconsidering here - there's a long distance between "someone believes in a harmful ideology" and "someone is an informant". So yes - there's ample room to talk with people.
"He who turns a sinner from the error of his way will save a soul from death and cover a multitude of sins" (James)
I think that's even true when a horrible ideology is gripping a nation. The Bolsheviks and Red Guards were not to be reasoned with by neighbors in their heyday. "The wise man sees trouble coming and hides himself."