Washington CNN Business  — 

A string of Democratic presidential candidates slammed the tech industry Tuesday night as they debated Silicon Valley’s effects on competition and political speech.

Entrepreneur Andrew Yang took aim at frontrunner Sen. Elizabeth Warren’s proposals to break up Big Tech, saying he would be in favor of forcing divestitures in some cases — but that simply creating new, smaller competitors won’t be enough to address the industry’s underlying problems.

“It’s not like any of us wants to use the fourth-best navigation app,” he said. “There is a reason why no one is using Bing today. Sorry, Microsoft (MSFT), it’s true.”

Yang also argued Americans should “share in the gains” enjoyed by tech companies because “our data is our property.

Warren fired back with a line she’s used before: That the enormous power companies such as Amazon (AMZN) hold in some markets, combined with their ability to use data to squeeze independent competitors, is a clear violation of antitrust law.

“You get to be the umpire in the baseball game, or you get to have a team, but you don’t get to do both at the same time,” she said. “We need to enforce our antitrust laws, break up these giant companies that are dominating — Big Tech, Big Pharma, Big Oil, all of them.”

Sen. Kamala Harris generally steered clear of the breakup question, other than to call “ridiculous” Facebook (FB) CEO Mark Zuckerberg’s claims that splitting up large tech platforms will only hamper efforts to combat online disinformation. Instead, she spent much of her time calling on her fellow candidates to support a ban on President Trump’s Twitter account.

Harris called out what she said was a “grave injustice” in Twitter’s policies, which grant greater leeway to newsmakers and world leaders than to average users.

It is an injustice, she said, “when rules apply to some but not equally to all, and in particular when the rules that apply to the powerless don’t apply to the powerful.”

Harris’ remarks came hours after Twitter clarified its policies in an attempt to explain what could lead the company to take action against a world leader’s tweet. Twitter said in a blog post that a world leader who sends a tweet that Twitter would otherwise take action on will get a pass if that tweet involves “fellow public figures,” “political issues of the day” or “foreign policy saber-rattling.”

Harris sought to draw a contrast between herself and other candidates who have not called for Twitter (TWTR) to act against Trump’s account, singling out Warren for not publicly backing her call. Warren ultimately acknowledged she does want Trump pushed off of Twitter (TWTR), but added that a bigger goal is to push him out of the White House. “That’s our job.” Warren then raised questions about her fellow candidates’ sources of financial support.

“If we’re going to talk seriously about breaking up Big Tech, then we should ask if people are taking money from the Big Tech executives,” she said. “If we’re going to talk seriously about breaking up big drug companies, we should ask if people are financing their campaigns by taking money from big drug executives.”

Warren earlier in the day vowed not to take contributions of $200 or more from executives in the tech, banking or finance industries.

Rep. Beto O’Rourke set his sights on Facebook and its decision to allow candidates to lie in advertisements on its platform. He called for imposing “very tough, very clear, transparent rules of the road” for social media platforms and compared them explicitly to traditional publishers.

“We would allow no publisher to do what Facebook is doing, to publish that ad,” referring to an ad by Trump’s campaign containing unfounded allegations against former Vice President Joe Biden. “Treat them like the publisher they are. That’s what I will do as president.” O’Rourke’s remark is part of a wider debate among critics of Silicon Valley over whether laws and rules designed for and by traditional media can or should apply to the tech industry. Last week, amid a spat with Warren, Facebook compared itself to broadcast TV stations that ran the Trump ad in compliance with federal law and regulations.

Sen. Cory Booker stopped short of committing to breaking up the tech industry. But he said that as president, he would appoint regulators who would take a stronger position on enforcing antitrust laws.

“We need regulation and reform,” he said, citing the tech companies’ involvement in the 2016 elections as an unwitting vector for foreign disinformation and election interference campaigns.