Why are Silicon Valley leaders criticizing Donald Trump?

Just as Supreme Court Justice Ruth Bader Ginsburg walked back her criticism of Donald Trump on Thursday, Mr. Trump faced a second critique – this time from prominent technology figures in Silicon Valley.

In an open letter signed by almost 150 current and former executives at firms such as Apple, Facebook, eBay, Twitter, and Wikipedia, the tech leaders didn’t mince words. Saying Mr. Trump “traffics in ethnic and racial stereotypes” and citing his comments on “shutting down” parts of the internet over security concerns, they argued that the presumptive Republican nominee “would be a disaster for innovation.”

While Silicon Valley leaders have often been somewhat dismissive of the billionaire businessman, the letter’s emphasis on close collaboration between government and the tech world also highlights the particularly close relationship the Obama administration has nurtured with Silicon Valley.

President Obama appointed the first chief technology officer in 2009, a chair that’s now occupied by Megan Smith, a veteran of Google. He has pushed for the Federal Communication’s approval of rules on net neutrality, a cause supported by many prominent tech figures.

His administration has also become something of a "revolving door" to the tech world, with former press secretary Jay Carney going to work at Amazon – where he has defended the company against reports about its working conditions – while campaign manager David Plouffe now works for the ride-hailing company Uber.

But that would likely change if Trump becomes president, the letter writers argue.

"We believe that government plays an important role in the technology economy by investing in infrastructure, education and scientific research," they write. "Donald Trump articulates few policies beyond erratic and contradictory pronouncements. His reckless disregard for our legal and political institutions threatens to upend what attracts companies to start and scale in America."

While Trump told The New York Times in June that “I have great respect for Silicon Valley,” he has also repeatedly taken shots at individual leaders and policies alike. At one point, his barbs aimed at Amazon’s Jeff’s Bezos over the company’s taxes prompted Mr. Bezos to propose launching Trump into space.

He has particularly been critical of H-1B visas, which are given to foreign professionals working in specific, skilled occupations, such as technology. “I know the H-1B very well,” Trump said at a Republican debate in March, Fast Company reports. “And it’s something I frankly use and shouldn’t be allowed to use it.”

But in Silicon Valley, immigration reform has emerged as a key focus for figures such as Facebook head Mark Zuckerberg, who founded an immigration reform-focused lobbying group called FWD.us.

Noting that 40 percent of Fortune 500 companies were founded by immigrants or their children, the letter’s signers write: “We believe that America’s diversity is our strength … We also believe that progressive immigration policies help us attract and retain some of the brightest minds on earth – scientists, entrepreneurs, and creators.”

The letter, which is signed by Tim Wu, who coined the phrase “net neutrality," also says that Trump’s call to “close up” or shut down the internet “demonstrat[es] both poor judgment and ignorance about how the technology works.”

The letter also singles out Trump’s “penchant to censor” media outlets and online platforms that criticize him – including The Washington Post, which is owned by Amazon’s Bezos.

Some of the rare tech world figures who say they support Trump have also noted that Trump’s brashness jibes with that of Silicon Valley – which could give them a reason to be weary.

“Silicon Valley is an extremely disruptive place,” Scott Slinker, an entrepreneur who donated $250 to the candidate last summer, told the Times. “But the one thing it doesn’t want disrupted is Silicon Valley. And so it’s pushing back on Trump.”