There are some interesting parallels between the two cases. In Eich's case, one of the reasons I decided I had been too hasty was that I didn't see anyone accusing him of actual discriminatory behavior as Mozilla's CTO. Apparently he had done well at keeping his politics out of the workplace. That seemed to me an argument for granting him the same consideration.
I don't really understand Thiel's politics. Some of the things he complained about in his RNC speech I understand and agree with as issues, though I don't understand why he thinks Trump is likely to address them. (I do understand why he thinks Hillary is unlikely to, though.) I haven't read any of Thiel's political writings, except for one widely-commented-on piece [0]. He doesn't sound to me like a racist; I'm less sure he's not sexist but I'll give him the benefit of the doubt on that. His reasons for supporting Trump seem to be highly idiosyncratic. If he's just trying to make the point that there's danger in giving the Democrats too much power, well, I don't disagree with that, though I probably disagree on how much is too much. Anyway, the point is, just as in Eich's case, there seem to be mitigating factors.
Well. I don't know the answer, but I offer the following thoughts. It's easier to demonize someone you don't know personally. That in itself suggests that ostracism should be a weapon of last resort.
But I understand your anger. If I were in YC and Thiel offered to invest in my startup, I don't know whether I would take his money.
[0] https://www.cato-unbound.org/2009/04/13/peter-thiel/educatio...