After Twitter recently sparked polarized reactions for flagging some of President Trump’s tweets (for inaccurate facts and “glorifying violence”), Facebook was slow to respond. Facebook cited a desire to stay out of politics; but by accepting advertising dollars for posts that violate its own content guidelines, Facebook has not been neutral.

It started as a murmur of dissent, but over the weekend the campaign to persuade brands to boycott Facebook ads for the month of July turned into a major crisis for the social media giant.

It began badly on Friday when Unilever, one of the world’s biggest advertisers, announced it was joining the Stop Hate for Profit campaign, which had already been backed by Verizon, Patagonia, and Ben and Jerry’s.

Facebook quickly tried to take action to stem the outward flow of ad dollars, announcing a new policy that would follow Twitter’s lead and begin labeling questionable content.

But it wasn’t enough.

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By Monday morning, more than 160 companies had announced they are stopping or pausing advertising on Facebook or social media more broadly.

Facebook makes 98% of its annual $70 billion revenue from advertising, and the impact of the campaign has not gone unnoticed on Wall Street. Facebook’s stock price tumbled more than 8% on Friday after Unilever’s announcement, wiping $56 billion off Facebook’s market value.

In pre-market trading Monday, Facebook shares were down a further 2.5%.