Peter Thiel’s $1.25 million donation to Donald Trump’s presidential campaign is driving away partners from Y Combinator, the Silicon Valley accelerator where he is a part-time adviser. Project Include, which works to improve diversity at tech companies, said today that it would no longer work with YC startups. "Thiel’s actions are in direct conflict with our values at Project Include," the group’s co-founder, Ellen Pao, wrote in a Medium post. "Because of his continued connection to YC, we are compelled to break off our relationship with YC."

Founded in 2005, Y Combinator has incubated some of the biggest tech companies of the past decade, including Airbnb, Dropbox, and Stripe. It faced a barrage of criticism over the weekend for refusing to dissociate itself from Thiel, who took an advisory role with the organization in 2015.

"Giving power to someone whose ascension and behavior strike fear into so many people is unacceptable."

In a series of tweets, YC’s president stood by Thiel. "Cutting off opposing viewpoints leads to extremism and will not get us the country we want," Sam Altman wrote. "Diversity of opinion is painful but critical to the health of a democratic society. We can't start purging people for political support."

In her post, Pao rejected the idea that Thiel’s donation could be dismissed as political speech. "We agree that people shouldn’t be fired for their political views, but this isn’t a disagreement on tax policy, this is advocating hatred and violence," she wrote. "Giving more power to someone whose ascension and behavior strike fear into so many people is unacceptable. His attacks on black, Mexican, Asian, Muslim, and Jewish people, on women, and on others are more than just political speech; fueled by hate and encouraging violence, they make each of us feel unsafe."

In a statement posted today, Altman said Thiel's support for Trump "has been a strain" on their relationship, but stood by the position he took on Twitter yesterday. "As repugnant as Trump is to many of us, we are not going to fire someone over his or her support of a political candidate," Altman wrote. " As far as we know, that would be unprecedented for supporting a major party nominee, and a dangerous path to start down (of course, if Peter said some of the things Trump says himself, he would no longer be part of Y Combinator)."

Update, 3:36 p.m. This article has been updated with Altman's comments today.