[Niks]

But should the head of a news corporation be publicly endorsing any political party or candidate?

[Bernard Marx]

I'll answer your question with another one: Should a newspaper endorse candidates on its editorial page? Most do. I don't think terms of employment invalidate the
First Amendment. I think it speaks well of a company that allows its employees to take political positions that might be considered "out of line" with the company's. (It also might be good PR as well!)