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The head of Silicon Valley's most famous startup factory says he's sticking with Peter Thiel, despite the billionaire investors' embrace of Donald Trump.

In a series of tweets Sunday night, Y Combinator president Sam Altman spelled out both his distaste for Trump — "an unacceptable threat to America" — and his backing for Thiel, who is both Altman's friend and a "part time partner" at Y Combinator.

Altman was responding to a new wave of criticism directed at Thiel, after Thiel announced he would donate $1.25 million to Trump's campaign. Thiel had previously repulsed much of Silicon Valley by embracing Trump and speaking at the Republican National Convention.

Some critics have called on Y Combinator, the incubator that has helped launch tech giants like AirBnb and Dropbox, to cut ties with Thiel in the wake of Thiel's announcement.

But Altman said that wouldn't happen. Y Combinator is "not going to fire someone for supporting a major party nominee," he tweeted. "That's a dangerous road to start down."

5) Cutting off opposing viewpoints leads to extremism and will not get us the country we want.

— Sam Altman (@sama) October 17, 2016

6) Diversity of opinion is painful but critical to the health of a democratic society. We can't start purging people for political support.

— Sam Altman (@sama) October 17, 2016

Altman's comments — which he said were personal, and not official Y Combinator messaging — shouldn't be that surprising.

They echo comments made late last week — before Thiel announced his donation — from Y Combinator founder Paul Graham, who said that if he were running the incubator, he would be "very leery of ditching people for their political views," and that "Peter is eccentric, but earnest. He seems to have a blind spot about Trump's character, but he is no surrogate."

This is a good time re-recommend the New Yorker's recent profile of Altman, which notes that Altman has "guns, gold, potassium iodide, antibiotics, batteries, water, gas masks from the Israeli Defense Force, and a big patch of land in Big Sur I can fly to" in case of a pandemic or some other kind of world-ending event.

Altman's backup plan, the New Yorker reports: Flying to Thiel's house in New Zealand.