I've been watching pg complain about Trump on Twitter with some interest. It is mind blowing to me that he has said nothing about Thiel so far.
If YC is saying Thiel can't be managed on that basis, he is a partner. And if he is a partner, YC can choose not to partner with him.
I could see both Goldman Sachs and YC operating under this mission statement.
As much as PG wants him to be, Thiel isn't an employee. He's a partner in a partnership, and partnerships have been dissolved for worse reasons than "offending partner is an opportunistic bigot".
This is a thing they have discussed before. If I were pg, I'd be bored with it by now.