It's not just the Republicans they'd have to worry about. For example, when the Washington Post tore apart Bernie Sander's claim that 500,000 Americans were bankruped by medical bills each year, he doubled down and demanded they retract the fact check - and a good chunk of the press sided with him on the basis that only Republican claims should be subject to this kind of fact checking. Some outlets even accused them of "partisan fact checking" and undermining democracy for not turning their fact checking into a partisan weapon.

This wasn't some minor detail either; he was suggesting his big expensive flagship policy could save hundreds of thousants of Americans a year from bankrupcy when it really couldn't. He stands by the bogus claim to this day. Now imagine what kind of headache it'd cause Facebook if they pulled a Sanders ad for using that or any other bogus debunked talking point...