Twitter CEO Jack Dorsey has learned that the fastest way to earn easy applause from progressives is to draw attention to the contrast between himself and Facebook head honcho Mark Zuckerberg. On Wednesday, Dorsey tweeted, “We’ve made the decision to stop all political advertising on Twitter globally. We believe political message reach should be earned, not bought.” This decision was an implicit but pointed rebuke to Facebook, which has been mired in controversy over its policy of not fact-checking political ads.

By taking a stance against political ads, Dorsey positioned himself as the anti-Zuckerberg. He was hailed as such by progressives. Representative Alexandria Ocasio-Cortez described Dorsey’s move as “a good call.” She added, “Not allowing for paid disinformation is one of the most basic, ethical decisions a company can make.” This sentiment was echoed by a leading centrist Democrat, Montana Governor Steve Bullock, who tweeted, “Good. Your turn, Facebook.”

While Facebook deserves all the scorn heaped on it, Twitter’s policy only creates a new set of problems. Despite their different paths, the two social media giants are both setting themselves up as the police of political discourse.

Democrats believe, with ample reason, that Donald Trump will use Facebook’s laissez-faire rules to spread lies on social media in his bid for reelection. In a New York Times op-ed on Thursday, Aaron Sorkin, who scripted The Social Network (2010), a biographical film about Zuckerberg, claimed the Facebook policy allows “crazy lies” to be “pumped into the water supply that corrupt the most important decisions we make together. Lies that have a very real and incredibly dangerous effect on our elections and our lives and our children’s lives.” Currently, Facebook is running an ad that claims, falsely and with genuine absurdist brio, that Joe Biden, with the aim of protecting his son Hunter Biden, gave a billion dollars to a Ukrainian official.

Zuckerberg argues that such surrealist slanders have to be allowed in the interest of free expression. The underlying contention is that Facebook is a platform, not a publisher, so can’t be held liable for false information and advertising in the way a newspaper or magazine would. But this self-conceptualization of Facebook as a neutral platform is at odds with reality. It functions for countless users as a source of news and, in fact, has supplanted many publications. In effect, Facebook wants to have the advantages of being a publisher, including collecting ad revenue, without the responsibilities.

The invocation of free expression is all the more disingenuous since Facebook doesn’t hesitate to reject political ads on arbitrary grounds. To protest its purported policy, Adriel Hampton has registered to run for governor of California in 2022 and tried to place dishonest ads on Facebook, including one claiming South Carolina Senator Lindsey Graham embraces the Green New Deal. Facebook has rejected Hampton’s ads, telling CNN, “This person has made clear he registered as a candidate to get around our policies, so his content, including ads, will continue to be eligible for third-party fact-checking.”

In making this decision, Facebook has made itself the arbiter of who is and isn’t a serious political candidate. The rule is that Facebook will give absolute free speech to politicians—but also gets to decide who is a politician. Facebook’s position is that it is acceptable to lie, as Trump does, to hold on to power—but not acceptable to lie in order to call attention to Facebook’s ad policy. In the guise of free speech absolutism, Facebook has arrogated to itself the right to define the parameters of political discourse.

The same problem of a private company’s policing the boundaries of political debate bedevils Twitter’s ostensibly different policy. As tech writer Will Oremus noted on OneZero, Twitter defines “political” in a way that will hamper labor unions, environmentalists, and activists of all sorts. Twitter defines political ads as “1/ Ads that refer to an election or a candidate, or 2/ Ads that advocate for or against legislative issues of national importance (such as: climate change, healthcare, immigration, national security, taxes).”

The second category creates a problem. Under prevailing conventions, advocating for consumption is never political speech, merely commercial speech. Conversely, advocating for changes in consumption or other aspects of the economic system is always political. Under Twitter’s rules, General Motors could buy an ad promoting a gas-guzzling car, but Greta Thunberg couldn’t buy an ad advocating climate action.

“This perverse dynamic isn’t limited to climate change,” Oremus observes. “Presumably, tech companies will still be able to run ads touting their commitment to user privacy, but watchdog groups will be barred from running ads suggesting that we need better privacy regulations. Big corporations will be able to boast about how they treat workers, but unions won’t be able to push for prevailing wage laws or workplace safety laws.”

No less than Facebook, Twitter has assumed a role that shouldn’t be held by a private business: the right to set the boundaries of political debate. In both cases, the root problem is that the proper authority for making such decisions, the democratically governed state, has abdicated responsibility. Social media needs to be regulated, with rules about what sort of political ads it can take. Failure to regulate leaves that crucial task in the hands of businessmen like Zuckerberg and Dorsey, who aren’t up to the job.

Dishonest political ads are only a small part of the problem of disinformation. The ads themselves are merely one corner of a much larger right-wing media ecosystem. That ecosystem extends from 4Chan and other fringe sites, where lies are often manufactured, to Fox News and Trump’s Twitter feed. If we see the ads as a node in this network, it becomes clear how limited their impact is. Most people in the older generation that is the core of the Republican base get their news mainly from television, not Facebook or Twitter. It’s Trump’s personal echoing of these lies, which are echoed in turn by Republican politicians and pundits, that is the problem.

Regulating Facebook and Twitter would be one step in the process of blunting the effect of lies in politics. Campaign finance reform would be another step. But the ultimate solution remains the political one of defeating Trump, creating a political coalition large enough to marginalize Trumpism—and rein in corporate power.