I feel like Thiel and any other people who deviate from the SF party line are the ones who should be thinking the way Popper does in that quote. I think that was how you meant it to be read but I'm not sure. That they're unable to reason with the people who seek to destroy them, because they've thought unthinkable thoughts.

I haven't read much about why Thiel supports Trump, but I'm willing to entertain arguments that whatever he likes about Trump (hypothetically economic policy?) is more important than his sexism. I feel like most people aren't.