Facebook has decided to keep an altered video of House Speaker Nancy Pelosi, D-Calif., on its site that makes her speech appear slow and slurred. Commenters, including President Donald Trump's personal attorney Rudy Giuliani, have used the video to call into question Pelosi's competence and mental state.

In a since-deleted tweet, Giuliani shared a link to the altered video and wrote, "What is wrong with Nancy Pelosi? Her speech pattern is bizarre." Giuliani later appeared to apologize on Twitter for sharing the video.

Experts told The Washington Post that the video, which is taken from Pelosi's appearance at a Center for American Progress event, appears to have been slowed down to about 75% of its original speed and modified for pitch. The alteration gives Pelosi an unnaturally slow, slurred speech pattern, which made several commenters wonder if she was drunk during the talk. An aide to the speaker called the attacks sexist and said Pelosi does not drink, a New York Times article reported.

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In a statement, a Facebook spokesperson said: "There's a tension here: we work hard to find the right balance between encouraging free expression and promoting a safe and authentic community, and we believe that reducing the distribution of inauthentic content strikes that balance. But just because something is allowed to be on Facebook doesn't mean it should get distribution. In other words, we allow people to post it as a form of expression, but we're not going to show it at the top of News Feed."

Facebook said it has begun limiting the video's distribution in the News Feed and adding additional context after one of its fact-checking partners reviewed the video and rated it as false. But the video has already been viewed and spread extensively. As of Friday, an altered version of the video remained on the Facebook page Politics WatchDog and had been viewed more than 2 million times. The Facebook spokesperson added early Saturday that users who view or share the video will see an alert that it's false.

Versions of the altered video could still be found Friday on Twitter as well. One user posted the altered video with the comment, "Please come get your drunk grandma @AOC #pelosi," and the video had been viewed more than 400 times. Twitter declined to comment.

Meanwhile, Google-owned YouTube removed the video from its platform, apparently determining the alteration did go too far. Like Facebook, YouTube has also suffered its share of criticism in the past for continuing to host content that walks the line of its policies.

"YouTube has clear policies that outline what content is not acceptable to post and we remove videos violating these policies when flagged to us," a YouTube spokesperson said in a statement to CNBC. "These videos violated our policies and have been removed. They also did not surface prominently. In fact, search results and watch next panels about Nancy Pelosi include videos from authoritative sources, usually at the top."

The video has drawn attention to the potential dangers of new technology that enables convincing alterations. Even though experts believe simple aspects like pitch and speed were changed in the Pelosi video, so-called deepfake technology uses artificial intelligence to modify videos even further. With the ability to mimic facial expressions, the possibilities for spreading misinformation could greatly expand.

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