How to handle political ads on social media has become a growing concern as the 2020 U.S. presidential election approaches.

Facebook has taken most of the heat, after refusing to remove an ad for President Trump's reelection featuring false information about his opponent Joe Biden.

While political ads on social media do not adhere to different rules than political ads on TV, they have come under specific scrutiny because of their unique ability to disseminate – broadly and rapidly -- bad information, and the platforms' inability to properly police them.

Compared to TV, online ads can spread lies at an alarming rate -- bolstered by machine-learning algorithms that can identify target audiences at enormous speed and scale.

In October, responding to a groundswell of concern, Twitter announced it would ban political advertising on its platform. Google and its subsidiary YouTube do not ban these ads, but the company last month came out with adjustments and clarifications to its policy, including limiting microtargeting of users.

In an interview on 60 Minutes, YouTube CEO Susan Wojcicki said the controversial Trump/Biden ad does not violate their policy.

60 Minutes correspondent Lesley Stahl asked Wojcicki, "Have you taken down any of President Trump's ads at all?" YouTube's CEO responded, "There are ads of President Trump that were not approved to run on Google or YouTube." When pressed for an example, Wojcicki added, "Well, they're available in our transparency report."

In response to concerns raised after the 2016 election cycle, Google and YouTube, like Facebook, keep a searchable archive of political ads that have run on the site.

60 Minutes reviewed the archive to learn more about President Trump's problematic political ads. We found that over 300 video ads were taken down by Google and YouTube, mostly over the summer, for violating company policy. But the archive doesn't detail what policy was violated. Was it copyright violation? A lie or extreme inaccuracy? Faulty grammar? Bad punctuation? It's unclear. The ads determined to be offending are not available to be screened. We found very little transparency in the transparency report.

"As you know, conservatives think that you discriminate against them," Stahl tells YouTube's Wojcicki, who replies: "Well, first of all there are lots of very successful conservative creators on YouTube... Our systems, our algorithms, they don't have any concept of understanding what's a Democrat, what's a Republican. They don't have any concept of political bias built into them in any way. And we do hear this criticism from all sides. We also have people who come from more liberal backgrounds who complain about discrimination. And so I think that no matter who you are, we are trying to enforce our policies in a consistent way for everybody."

The archive does detail how many days the ad ran on the platform before it was taken down, approximately how much Google was paid and how many impressions it received. Typically, ads ran a few days before being yanked, suggesting they reached the target audience before removal.