In the aftermath of a violent protest in Charlottesville, Va., that left three dead and thrust neo-Nazis, the Ku Klux Klan and other white nationalists back into the public eye, tech companies big and small have turned their back on far-right extremists by cutting off access to revenue and canceling service — effectively banishing them to the far corners of the Internet.

The Daily Stormer, a neo-Nazi website, went offline. PayPal stopped transactions that benefited hate groups and their supporters. And OkCupid revoked the dating privileges of known white supremacists.

While some antiracist activists and tech leaders applauded the impact the digital ice-out would have on extremists’ reach and revenue, others worried that tech firms may have gone too far: Could they do the same to any group that challenges popular ideals or opposes the interests of Silicon Valley?

“The same policies against hate speech or hate groups or terrorist propaganda that are leading companies to take down the Daily Stormer and its folk are routinely used against groups on all sides of the political spectrum that don’t advocate violent ideology whatsoever,” said Emma Llansó, the director of the Free Expression Project at the Center for Democracy and Technology. “Any tool that enables censorship online can be used against potentially everyone — regardless of ideology.”

White nationalists and free-speech activists have begun building alternatives to the mainstream Internet in an effort to operate outside the rules and norms of Silicon Valley, on networks where hate speech and extremist organizations can exist unchecked.

But there are significant drawbacks, said Cody Wilson, who helped to create Hatreon, an alternative to the better-known Patreon, a website that allows content creators to receive financial support from users.

“No one truly wants to rebuild 20 years of Internet infrastructure so they don’t have to engage in these full-scale social purges,” said Wilson. “There’s not a lot of money or talent behind the so-called ‘alt-tech.’ This isn’t a thing where we’re like, ‘Oh, we’re going build a whole new world.’ It doesn’t work that way.”

Wilson doesn’t align himself politically with white nationalists or far-right extremists. But he believes that they, too, should have a forum to express themselves.

Hatreon, which has about 1,000 users, was booted off of its infrastructure provider, DigitalOcean, Friday amid a widespread purge of hate groups from the Internet’s most prominent gatekeepers.

Several online civil rights groups, including the Center for Democracy and Technology and San Francisco advocacy group the Electronic Frontier Foundation, have questioned the power of big tech firms and cautioned those who cheer the dismantling of Nazi websites that they could be next.

After terminating its contract with the Daily Stormer, Matthew Prince, the CEO of website security firm Cloudflare, said in an interview with TechCrunch that the power Internet companies have is troubling, and without a system in place to regulate decisions that result in censorship, it’s unlikely those decisions will be made objectively.

Privately owned tech companies are not subject to the First Amendment, which ensures the right to speech free from government censorship. Most, instead, operate in accordance with their own terms of service.

But even then it can be hard to tell whether a company is implementing its rules fairly or singling out certain people or groups that it may not like, Llansó said.

“We need more transparency across the board,” she said. “It’s kind of hard to talk about content moderation when we still don’t have very good information about what social media platforms are actually doing.”

Even the open Web, a supposed free-for-all, has posed challenges for far-right groups. GoDaddy and Google refused to manage the Daily Stormer’s Internet domain, forcing it to bounce around to several different domains — including one on the dark Web and another in Russia — before resurfacing with the unlikely address dailystormer.lol through the domain registrar NameCheap.

NameCheap did not immediately respond to a request for comment, though the company’s terms of service explicitly outlaw “hate sites.”

Discord, a voice chat service popular among video game enthusiasts that had been instrumental in organizing far-right extremists, axed several accounts, chat rooms and servers affiliated with neo-Nazi sentiments or white nationalist groups.

Google also banned social network Gab, billed as the far-right’s version of Twitter, from its Android app store Thursday.

“Our online community leans libertarian, small-c conservative, and anti-corporatist left,” Gab spokesman Ustav Sanduja wrote in an email.

Since then, the social network has raised $400,000 from its users, Sanduja said, pushing its total contributions since July to more than $1 million. Gab, which has 207,000 users, was founded by Bay Area entrepreneur Andrew Torba, who considers the social network a haven for Internet separatists.

Twitter, YouTube, Reddit and Facebook have long been the subject of criticism both for suspending and banning accounts because of the content they publish on those sites and also for not doing enough to combat hate speech and harassment.

Facebook and YouTube have recently announced plans to use artificial intelligence and machine learning to better identify — and more quickly suspend — groups that promote hate speech and white nationalist ideologies on the social networks.

“We all felt this righteous indignation after what happened (in Charlottesville), and fair enough,” Hatreon’s Wilson said. “But look, if some radical San Francisco LGBT group got kicked off the Internet for violating terms of service, we would all be having a very different conversation.”

Marissa Lang is a San Francisco Chronicle staff writer. Email: mlang@sfchronicle.com Twitter: @Marissa_Jae