Facebook CEO Mark Zuckerberg defended Facebook board member Peter Thiel’s support of Republican presidential nominee Donald Trump in a post that invoked the importance of “diversity” for the social media company.

“We care deeply about diversity. That’s easy to say when it means standing up for ideas you agree with. It’s a lot harder when it means standing up for the rights of people with different viewpoints to say what they care about,” Zuckerberg wrote in a post visible only to Facebook employees, a photograph of which was shared on Hacker News on Tuesday.

“We can’t create a culture that says it cares about diversity and then excludes almost half the country because they back a political candidate,” Zuckerberg continued. “There are many reasons a person might support Trump that do not involve racism, sexism, xenophobia or accepting sexual assault.”

Facebook confirmed the authenticity of the post, but has not responded to repeated requests for comment on Thiel from the Guardian.

One of the co-founders of PayPal, Thiel was an early Facebook investor who maintains deep connections and influence in Silicon Valley. His positions at Facebook and other companies have come under increased scrutiny since the New York Times reported this weekend that he planned to donate $1.25m to Trump’s campaign.

Thiel had previously served as a delegate for Trump and delivered a keynote address at the Republican national convention. He also wrote an op-ed for the Washington Post in which he praised the Trump campaign’s success at “saying things that made sense to voters”.

But news of Thiel’s donation to Trump’s campaign, which came after numerous women made allegations of sexual assault against Trump, let loose a new wave of criticism of Thiel within the tech industry.

Project Include, an organization that seeks to promote diversity and inclusion in the tech industry, cut ties with Y Combinator on Monday, citing the influential startup incubator’s failure to remove Thiel as a “part-time partner”.

Sam Altman, the president of Y Combinator, has compared Trump to Adolf Hitler, but he too invoked “diversity” in defending his decision not to disassociate from Thiel.

Thiel is one of eight members of Facebook’s board of directors. All of the directors are white and six of them are men.

According to its July 2016 “diversity update”, Facebook’s staff is 52% white and 67% male. The company’s workforce is just 2% black, 4% Latino and 33% female.

In 1998, Thiel co-authored the book The Diversity Myth: Multiculturalism and Political Intolerance on Campus, which criticized Stanford University’s valuing of campus diversity. According to the publisher’s synopsis, the book also argued that “campus hysteria over date rape – a phenomenon that has been greatly exaggerated – [was] leading to more unjustified restrictions of student liberties”.

Earlier this year, Zuckerberg criticized another board member, Marc Andreessen, for his statement on Twitter that appeared to support colonial rule in India. Zuckerberg wrote then that Andreessen’s views “do not represent the way Facebook or I think at all”.