Just because it hasn't happened in these cases doesn't mean there isn't a case for it yet. It's very complex. That's why people pay lawyers.
The point I'm making here is that the business world isn't a universe where people can 100% of the time support an outspoken racist, anti-semitic, Islamaphobic, misogynistic, sexual predator authoritarian who wants to put an end to American democracy.
Imagine if the CEO of Coca Cola did what Peter Thiel did. You wouldn't think he wouldn't be out on his butt?
It's a case by case basis, but saying "business therefor you can say and support whoever you want" is wrong. It's up to YC to do as they wish, I just wanted to point out that things are a little more nuanced here.