Facebook employees are urging Mark Zuckerberg to rethink his stance on allowing politicians to lie in political ads. In an open letter to company executives obtained by The New York Times, more than 250 people said the policy — which exempts such ads from Facebook’s third-party fact-checking standards — threatens what the company stands for:

Misinformation affects us all. Our current policies on fact checking people in political office, or those running for office, are a threat to what FB stands for. We strongly object to this policy as it stands. It doesn’t protect voices, but instead allows politicians to weaponize our platform by targeting people who believe that content posted by political figures is trustworthy.

They added that it fuels mistrust of the platform and “it communicates that we are OK profiting from deliberate misinformation campaigns by those in or seeking positions of power.”

Employees urged executives to restrict how politicians are able to target potential voters. Today, they are able to segment users based on how likely they are to vote or how susceptible they might be to a potential message — tactics made infamous by the political consulting firm Cambridge Analytica. “These ads are often so micro-targeted that the conversations on our platforms are much more siloed than on other platforms,” employees said. Facebook already applies such restrictions to ads related to housing, education, or credit, to stop potential discrimination.

Facebook’s ad policy has been under fire since September, when vice president of communications Nick Clegg attempted to explain why the company would no longer “referee political debates” by fact-checking political ads. Elizabeth Warren claimed the move was a clear sign they were taking “deliberate steps to help one candidate intentionally mislead the American people,” then escalated things further by posting an ad claiming Mark Zuckerberg and Facebook endorsed Trump. “We intentionally made a Facebook ad with false claims and submitted it to Facebook’s ad platform to see if it’d be approved. It got approved quickly and the ad is now running,” she tweeted.

Last week, the company took down an ad that falsely claimed Lindsey Graham (R-SC) supported the Green New Deal. The Really Online Lefty League, a liberal PAC, ran it to test whether Facebook’s policy applied to political organizations. Because the ad was purchased by a third-party group, it was subject to a stricter fact-checking policy than posts by the candidates themselves.

Two weeks ago, Mark Zuckerberg gave a speech at Georgetown University where he tried to crystallize his thoughts on free speech and his company’s role in moderating political conversations. The speech was widely criticized by the left and right; both parties thought Zuckerberg was shirking his responsibility for helping to spread misinformation. Now, it seems even his own employees agree.