Last week, before the white supremacist “Unite the Right” rally in Charlottesville, Virginia, Airbnb did something few tech companies had done before: it flat-out banned white supremacist users from accessing its platform to rent out rooms or homes around Charlottesville while they attended. C.E.O. Brian Chesky defended the move as a way to censure behavior that is “antithetical to the Airbnb Community Commitment,” and said the company will take action in the future to pre-emptively ban users booking lodging for similar events. “Violence, racism, and hatred demonstrated by neo-Nazis, the alt-right, and white supremacists should have no place in this world,” Chesky said.

In the days since the rally, which killed one counter-protester, a growing number of other Silicon Valley companies have made the decision to purge users and groups promoting hate speech. GoDaddy, which had hosted neo-Nazi Web site the Daily Stormer, cut ties with the Web site for inciting violence, telling it to find another host. The Daily Stormer went to Google, which promptly kicked the Web site off of its own hosting services, too. Cloudflare, enterprise software company Zoho, and e-mail newsletter service provider SendGrid also separated themselves from the Daily Stormer. The site quickly made its way to the “dark web” before ending up in Russia.

Prior to Charlottesville, there had been some apprehension among big tech companies over whether to take more forceful action against hate groups. For as much as their speech is detestable, it is still ostensibly free. Twitter and Facebook have touted themselves as spaces for free expression, though they began to set limits in recent years as trolls and extremists took advantage of both platforms. But Charlottesville brought a new level of moral clarity—or at least moral outrage—to a long-simmering debate in Silicon Valley. Twitter quickly deactivated an account associated with the Daily Stormer and a popular far-right social-media star who goes by @Millennial_Matt; Facebook removed an event page for the rally over the weekend and has prohibited people from sharing a Daily Stormer article about the counter-protester who was killed on Saturday.

Some companies took more stringent action. Uber permanently banned James Allsup, a popular white supremacist figure online, after he and two friends got into a fight with a black Uber driver the day before the Charlottesville rally. Uber personally thanked and honored the driver, and asked her to give a speech in front of thousands of Uber employees. Both Apple Pay and PayPal have cut off white supremacists from using their services. Discord, a voice-chat app for gamers that’s become popular with white supremacists, cracked down on the far-right contingent of its user base after the Charlottesville rally. GoFundMe and Kickstarter both prohibit crowdfunding efforts for white supremacists on their platforms. Spotify is removing music made by artists considered “hate bands” by the Southern Poverty Law Center. Squarespace decided to remove pages belonging to Richard Spencer’s think tank and other “alt-right Web sites,” too.

It’s easy to justify cutting off service when it comes to Nazis. It’s harder to know where tech companies should draw the line in other, more ambiguous cases, as many tech leaders are fully aware. Cloudflare C.E.O. Matthew Prince said as much in an internal memo to his employees when he decided to ban the Daily Stormer this week. “Let me be clear: this was an arbitrary decision,” he wrote. “It was different than what I’d talked talked with our senior team about yesterday. I woke up this morning in a bad mood and decided to kick them off the Internet. . . . After today, make no mistake, it will be a little bit harder for us to argue against a government somewhere pressuring us into taking down a site they don't like.” Prince had previously been something of a free speech absolutist. “A website is speech. It is not a bomb,” he said in 2013. “One of the greatest strengths of the United States is a belief that speech, particularly political speech, is sacred.”

Facebook’s Mark Zuckerberg made a similar comment regarding how Facebook is grappling with hate speech. “Debate is part of a healthy society,” he said in a Facebook post Wednesday. “But when someone tries to silence others or attacks them based on who they are or what they believe, that hurts us all and is unacceptable.” It’s a fine sentiment, but also one that’s hopelessly vague and will be impossible to enforce without someone feeling hurt. For now, Silicon Valley has decided that taking sides in those fights is righteous, as long as they are on the right side. That may work when it comes to purging Nazism in 2017, but it’s hard to imagine it won’t set a precedent for how companies choose to police content in the future.