Great discussion to be had, but you seem to be working this towards a slippery slope argument that if we don't choose to do business with billionaires to give millions and stump at the RNC convention, it won't be long before we're firing 43% of the workforce.
I can accept that YC may choose not to cut Mr. Thiel loose, but I'm not convinced that there is a moral imperative not to cut him loose.
Where does it stop though? Where is the line where you say "I disagree with you, therefore I will not associate with you"? There is definitely a line. Supporting a candidate who says a lot of stuff probably isn't it. I knew people who were against Obama because his religious leader had said something that could be construed to be pro-satan. Obama is not a 100% mirror (or even a tiny bit) that religious leader. Not supporting Trump for what he says seems fine - he's 100% responsible for what he says. Not supporting someone else, who supports Trump, is not OK. That other person has separate thoughts, and input from hundreds/thousands of other people. It's like saying if you support someone who supports Clinton, you support top secret emails being on everyone's private servers. It's a tiny slice of the whole. Or, "don't throw the baby out with the bath water".
I can accept that YC may choose not to cut Mr. Thiel loose, but I'm not convinced that there is a moral imperative not to cut him loose.