WhatsApp co-founder Brian Acton appeared as a speaker at a class at Stanford University earlier this week, where he spoke about the decision to sell the company to Facebook, and urged students to delete their Facebook accounts.

According to Buzzfeed News, Acton spoke during an undergraduate course called Computer Science 181 alongside another former Facebook employee, Ellora Israni, founder of She++. During the class, Acton spoke about why he sold Whatsapp to Facebook in the first place, and why he left, and criticized the drive to prioritize monetization over user privacy.

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During his talk, he noted that major technology and social media companies like Apple and Google have struggled to moderate their content. “These companies are not equipped to make these decisions,” he said. “And we give them the power. That’s the bad part. We buy their products. We sign up for these websites. Delete Facebook, right?”

Acton has been a vocal critic of Facebook since leaving the company in 2017 over issues with Facebook’s desire to monetize its services. This also isn’t the first time that he’s called for people to delete their accounts: he said the same thing last year, following the Cambridge Analytica scandal.