There are three good articles on the difficulty of controlling white supremacists' and terrorists' communication over the Internet.
Here's one:
Legal Shield for Websites Rattles Under Onslaught of Hate Speech
Section 230 says that "No provider or user of an interactive computer service shall be treated as the publisher or speaker of any information provided by another information content provider." This federal law preempts any state laws to the contrary: "[n]o cause of action may be brought and no liability may be imposed under any State or local law that is inconsistent with this section." The courts have repeatedly rejected attempts to limit the reach of Section 230 to "traditional" Internet service providers, instead treating many diverse entities as "interactive computer service providers."
Aug. 6, 2019
When the most consequential law governing speech on the internet was created in 1996, Google.com didn’t exist and Mark Zuckerberg was 11 years old.
The federal law, Section 230 of the Communications Decency Act, has helped Facebook, YouTube, Twitter and countless other internet companies flourish.
But Section 230’s liability protection also extends to fringe sites known for hosting hate speech, anti-Semitic content and racist tropes like 8chan, the internet message board where the suspect in the El Paso shooting massacre posted his manifesto.
The First Amendment protects free speech, including hate speech, but Section 230 shields websites from liability for content created by their users. It permits internet companies to moderate their sites without being on the hook legally for everything they host. It does not provide blanket protection from legal responsibility for some criminal acts, like posting child pornography or violations of intellectual property....
On Wednesday, the United States Court of Appeals for the Second Circuit affirmed a lower court’s ruling that Facebook was not liable for violent attacks coordinated and encouraged by Facebook accounts linked to Hamas, the militant Islamist group. In the majority opinion, the court said Section 230 “should be construed broadly in favor of immunity.”
Second Circuit Rules That Section 230 Bars Civil Terrorism Claims Against Facebook (EFF)
NYT also has an article on how the web forum 8chan, where the El Paso mass murderer posted his "manifest", became a haven for white supremacists. 8chan relied on Cloudshare, a web performance and security company, to provide its service to keep it from shutting down. Cloudshare, who had previously taken a neutral stance on the content in any of the businesses using its services, changed their minds after El Paso.
"The rationale is simple: they have proven themselves to be lawless and that lawlessness has caused multiple tragic deaths,” wrote their CEO Matthew Prince. “Even if 8chan may not have violated the letter of the law in refusing to moderate their hate-filled community, they have created an environment that revels in violating its spirit."
On Capitol Hill, Facebook and other social media giants have regularly been called to testify with the latest cry that their monitoring of content on their site is unfairly targeting conservative groups. Trump has said that he will monitor that "censorship". Also, a bill has been introduced that will make an exception to 230 making companies liable for child pornography content posted on their site.
Considering both terrorist group communications and the changes in our culture and values, 230 and court decisions on free speech make it difficult to shut down racist and terrorist, for instance, content that weakens our ability to take action.