Some of my most libertarian/pro-gun friends have not been shy about their political views and it hasn't hurt their tech careers at all. They are far more welcome here than liberals are in other parts of the country.
It seems to me, from personal experience, that the people who feel alienated are the ones who bring politics to work in an overbearing contrarian way, seeking to cause offense under the guise of "debate," and then pretend to be shocked when people don't want to put up with their shit. Work is for working; it's not a debating society, and especially not when the debating is done in bad faith.
Peter Thiel has been more politically vocal than most, and he is vocal about things he knows to be unpopular. He can't be surprised that people who disagree with him are also vocal. If he can't take the heat he should stay out of the kitchen.