Mark Zuckerberg defended Facebook’s policy of letting politicians lie in political ads — along with free speech more broadly — in a speech today at Georgetown University. “I don’t think it’s right for a private company to censor politicians” he said.

Zuckerberg’s speech, which amounted to a rallying cry for the First Amendment during a time when speech rights are under siege globally, acknowledged the fact that Facebook profits off misinformation — but said that’s not why the company decided to allow inaccurate ads to remain on the platform:

Given the sensitivity around political ads, I’ve considered whether we should stop allowing them altogether. From a business perspective, the controversy certainly isn’t worth the small part of our business they make up. But political ads are an important part of voice — especially for local candidates, up-and-coming challengers, and advocacy groups that may not get much media attention otherwise.

Throughout the speech, Zuckerberg couched Facebook’s policies as the result of moral choices rather than business decisions. “Banning political ads favors incumbents and whoever the media covers,” he said, noting the solution is to monitor who is posting the content rather than the content itself. “You can still say controversial things,” he added, “but you have to stand behind them with your real identity and face accountability.”

Zuckerberg’s comments come at a time when Facebook is under fire for helping spread misinformation and is being investigated by the Justice Department and 40 state attorneys general for possible antitrust violations. Politicians from Josh Hawley (R-MO) to Elizabeth Warren (D-MA) are calling for the company to be broken up.

Warren has been on the forefront of calling out the company’s permissive ad policies, which she says have turned the company into a “disinformation-for-profit machine.” After Facebook modified its policy to exempt political ads from fact-checking, she ran an ad falsely claiming that Zuckerberg had endorsed Trump to illustrate her point.

To Zuckerberg, the fallout from Warren is the cost of defending free expression. “I don’t think most people want to live in a world where you can only post things that tech companies judge to be 100 percent true.” he said. “I believe we should err on the side of greater expression.”