Facebook CEO Mark Zuckerberg defended the company's decision not to fact-check political ads, telling investors on an earnings call Wednesday that political advertising was free speech while downplaying its role as a moneymaker for Facebook.

He also minimized the importance of political ads to Facebook's bottom line, saying, "We estimate that these ads from politicians will be less than 0.5% of our revenue next year."

"To put that in perspective, the FTC fine that critics said wasn't big enough to change our incentives was 10 [times] bigger than this," Zuckerberg added.

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Yet Facebook is projected to take in $84 billion in revenue in 2020, according to FactSet estimates. Half of 1% of that figure comes to $420 million.

"Ads can be an important part of voice, especially for candidates and advocate groups that the media might not cover," Zuckerberg told investors, defending his decision hours after Twitter announced it would ban all political ads starting in three weeks.

Facebook reported solid third-quarter results Wednesday, showing steady growth in its user base despite broad regulatory threats and criticism over its power and negative effects on society.

The company earned $6.09 billion in the July-September quarter, up 19% from $5.14 billion in the same period a year earlier. Revenue grew 29% to $17.65 billion from $13.73 billion.

Facebook ended the quarter with 2.45 billion monthly users, up 8% from a year earlier. It also said that about 2.8 billion people use at least one of its services — Facebook, Messenger, WhatsApp or Instagram — at least once a month.

The company faces several government investigations for alleged anti-competitive behavior, including probes by the Federal Trade Commission and 46 state attorneys general.

Zuckerberg last week faced pointed questioning from members of Congress last week when he testified about the company's plans for a digital cryptocurrency.

Investors sent Facebook's stock price up 4% to about $196 a share in after-hours trading following the earnings report.

The Associated Press contributed reporting.