Facebook CEO Mark Zuckerberg has issued a public response to a tweet earlier Wednesday from President Trump, who claimed that the social network “was always anti-Trump” during the 2016 presidential campaign. “Trump says Facebook is against him. Liberals say we helped Trump,” Zuckerberg wrote. “Both sides are upset about ideas and content they don't like. That's what running a platform for all ideas looks like.”

Zuckerberg’s statement comes on the same day that Facebook, Google, and Twitter have been asked to testify before Congress on November 1st, where they’ll face questions about Russia’s meddling in the 2016 election and how it might have used their platforms to spread misinformation in an attempt to influence the outcome.

Facebook was always anti-Trump.The Networks were always anti-Trump hence,Fake News, @nytimes(apologized) & @WaPo were anti-Trump. Collusion? — Donald J. Trump (@realDonaldTrump) September 27, 2017

Facebook’s chief executive was critical of that notion in the days immediately following the election; Zuckerberg said it was “pretty crazy” to believe Facebook might’ve helped to swing the presidential race. But it has since been revealed that Russia spent over $100,000 on political ads on the Facebook platform with the intention of “amplifying divisive social and political messages.” Facebook groups associated with Vladimir Putin may also have organized pro-Trump rallies on US soil. “After the election, I made a comment that I thought the idea misinformation on Facebook changed the outcome of the election was a crazy idea,” Zuckerberg said today. “Calling that crazy was dismissive and I regret it. This is too important an issue to be dismissive.” That’s the most direct about-face that Zuckerberg has made on his controversial November remarks.

The company has also agreed to provide Congress with Russia-linked ads that moderators told The Verge they were left unprepared to catch, and Zuckerberg on Wednesday delivered a statement to viewers on Facebook Live announcing that the social network will no longer accept untraceable ads. “We’re going to bring Facebook to an even higher standard of transparency,” he said. “Not only will you have to disclose which page paid for an ad, but we will also make it so you can visit an advertiser’s page and see the ads that they are currently running to any audience on Facebook.”

But Zuckerberg is still very, very insistent that Facebook is doing far more to help the democratic process than to harm it. “The data we have has always shown that our broader impact — from giving people a voice to enabling candidates to communicate directly to helping millions of people vote — played a far bigger role in this election.” Facebook hasn’t to this point shared any of that data with its users and the public at large, but here are some of Zuckerberg’s arguments:

- More people had a voice in this election than ever before. There were billions of interactions discussing the issues that may have never happened offline. Every topic was discussed, not just what the media covered. - This was the first US election where the internet was a primary way candidates communicated. Every candidate had a Facebook page to communicate directly with tens of millions of followers every day. - Campaigns spent hundreds of millions advertising online to get their messages out even further. That's 1000x more than any problematic ads we've found. - We ran "get out the vote" efforts that helped as many as 2 million people register to vote. To put that in perspective, that's bigger than the get out the vote efforts of the Trump and Clinton campaigns put together. That's a big deal.

“We will continue to work to build a community for all people,” he wrote today. “We will do our part to defend against nation states attempting to spread misinformation and subvert elections.”