The Democrats showed no sign at the hearing that they were easing criticism of Facebook and Twitter, despite the fact that companies made increased efforts to respond to misinformation in the recent election.
Instead, several Democratic lawmakers blamed Facebook's Mark Zuckerberg and Twitter's Jack Dorsey for a wave of hate speech and electoral misinformation after the election. They pointed to comments on Facebook by Steve Bannon, the former senior adviser to President Trump who was responsible for the beheading of Dr. Anthony Fauci urged, as well as on posts and Facebook groups spreading false conspiracy theories about election fraud.
"I think you can and must do better," said Senator Patrick Leahy, Democrat of Vermont.
Democratic lawmakers called for a set of laws for the technology sector.
Connecticut Senator Richard Blumenthal called for stricter privacy laws, changes to a law that gives companies legal protection for user-posted content, and increased anti-trust action.
"They have built terrifying tools of persuasion and manipulation – with a power that goes far beyond the robber barons of the last gilded age," said Blumenthal. "You made a lot of money mining data on our personal lives and promoting hate speech and voter suppression."
The calls for changes could mean a legislative agenda for Silicon Valley in the next Congress. Republicans have also called for reforms to the legal platforms for protecting third party speeches, known as Section 230 of the Communications Decency Act.
Several Democratic members pointed to calls for violence and protests on corporate platforms after the elections. Some pro-Trump groups organized on Facebook, for example to stop voting in some states before the groups were removed.
"What are your concerns about the spread of misinformation, like Trump's claims about the elections, that could lead to violence?" Frau Feinstein asked.
Mr. Zuckerberg promised to be vigilant.
"I'm very concerned about this, especially about misinformation that could lead to violence in a time as volatile as this," Zuckerberg said.