If you're saying Sam should come out and say he disagrees with Thiel, he's already said he finds Trump repugnant. Are you saying that in addition to this, he also has to say, "I now draw attention to the fact that by opposing Trump, I am hereby disagreeing with my partner who supports him"? Why? And could it possibly also be because YC has other people in it, and disavowing a partner of YC by himself would be acting irresponsibly toward his partners?
If you're saying YC as an institution should disavow Thiel's actions, is every company expected to choose a political stance, then disavow any partners who act against it? For that matter, it's disingenuous of you to point to an individual's tweets denouncing Trump, then to the fact that his organization hasn't done the same, and call it a lack of moral courage.
It's also disingenuous to suggest, as you do in your tweets where you warn women and Muslims against joining YC, that because one of their partners donated to Trump and spoke at his convention, YC as an institution is now somehow poisoned with the views typical of a Trump supporter. Presumably Thiel was added as a partner for the simple reason that he is a valuable source of advice for startups. He can still be one as a keynote speaker for Trump. Besides, most people who endorse candidates, even people who act as keynote speakers, don't agree completely with their candidate, which further weakens your argument.
Finally, I sometimes read your tweets, and I noticed you tweeted https://twitter.com/Pinboard/status/787756601281085440 to Paul Graham's wife. Your usual sense of humor becomes weirdly aggressive when you write about YC, like you really want to pick a fight. What's your problem with them?