Person -> SOPA
Person -> Trump -> Sexism/Racism/etc
Thiel doesn't support Trump because he's racist/etc, he does it in spite of that. That doesn't make Thiel right, however it is an important distinction. If Thiel said or did anything racist/sexist/etc, he'd be out of YC. It's a slippery slope to start firing people because someone they support supports something you don't like.
After all, Clinton supports SOPA, and Sam just endorsed her.