Following Donald Trump’s presidential election victory last Tuesday, a partner at Peter Thiel’s venture capital firm has publicly expressed his fears of a Trump presidency, breaking with the contrarian tech billionaire’s staunch support for the Republican real estate mogul.

Just as Thiel joins Trump’s White House transition team, Bloomberg reports that Geoff Lewis of Founders Fund spoke out against the President-elect, in a blog post published on Sunday titled “Turn On Reality.”

“It seems irrefutable to me that the Trump campaign’s truths, untruths, and things left strangely unsaid have left millions of Americans feeling vulnerable and voiceless,” Lewis wrote. “Where fear flourishes, violence follows.”

Much of the current state of affairs, the venture capitalist suggested, has to do with an increasing public obsession with social media. “Social media has become Reality TV 2.0,” he wrote. “Everyone gets to be the star of a custom designed digital echo chamber.”

While Thiel is an investor and board member of Facebook fb , the biggest social media network of them all, Lewis suggested that social networks have resulted in an increasing cycle of political reinforcement among users of similar viewpoints, creating ever-greater polarization.

For example, he wrote that “for every Clinton voter who couldn’t name a single Facebook friend supporting Trump, there was a Trump voter who couldn’t name a single Facebook friend supporting Clinton.”

Facebook’s founder Mark Zuckerberg refuted criticism that the spread of fake news on his network might have swayed the election’s outcome in a note published Saturday, after first suggesting Thursday that it was “a crazy idea.”

In his later note, Zuckerberg wrote that it was “extremely unlikely hoaxes changed the outcome of the election in one direction or the other.”

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In his post on Medium, Lewis said that he fears a Trump presidency. “If we take Trump seriously, it may not be safe for me to write a post like this a year from now,” he wrote, even suggesting that “if some of the most frightening rumors circulating already are true, then I will face retaliation just for writing these words today.”

Noting that fear “is spreading now in many circles” after the election, Lewis calls for people to find more common ground with each other, writing that “the antidote to fear is empathy.”