[uola]

As far as I know, freedom of speech protects you from the government. Since YC is not the government freedom of speech isn't applicable, but anti-discrimination or employment law could be. In fact if the government would limit YCs freedom to not associate with Theil, as guaranteed by freedom of speech, that could technically be a greater violation of rights. This is why some libertarians think that private discrimination should be legal.

> In short, we should condone private — but not government — discrimination, even if the rationale is that a service provider simply doesn’t want to deal with the persons seeking service. That rationale — however offensive it may be in some circumstances — is implicit in our right not to associate, which is the flip side of our constitutional right of association, guaranteed by the First Amendment.

http://www.cato.org/policy-report/marchapril-2016/libertaria...

But I don't have the best understanding of US laws.