You can view the Stormers and their ilk as fringy “losers,” as the White House strategist Stephen K. Bannon described them this week. But the internet can rocket the fringe to the front and the center in an instant. The Stormers certainly saw the rally as their step out of the web’s shadows, one made possible by the following they had built online.

As a Daily Stormer “feature writer” says on the appropriately praised “Vice News Tonight” documentary on the rally, “As you can see we are stepping off the Internet in a big way.” Putting a finer point on it, he tells the Vice correspondent Elle Reeve, “People realize they are not atomized individuals. They are part of a larger whole because we have been spreading our memes. We have been organizing on the Internet, so now they’re coming out.”

That came to an end this week when GoDaddy said it would no longer host The Daily Stormer because its article mocking Ms. Heyer “could incite violence, which violates our terms of service.” The Daily Stormer hit the same problem when it moved its domain to Google, where the “terms of service” also prohibit content that could incite violence. And then Google booted The Stormer from YouTube.

A cascade of others followed: Visa, MasterCard and Discover said they were reassessing or ending their financial service agreements with extremist sites; GoFundMe shut down campaigns supporting the man accused of killing Ms. Heyer, James Fields; OKCupid banned the white supremacist Chris Cantwell for life; the streaming music service – and New York Times partner — Spotify told Billboard on Wednesday that it was removing a collection of bands that the Southern Poverty Law Center had identified as “hate bands.”

Then again, that list had been out for three years.

As we’ve seen time and time again in recent months, it often takes an extreme moment to push the platforms to address extreme content.

Part of the problem is logistical: There is so much material flooding the platforms that the most dangerous items can slip through.