The danger inherent in such industries "policing" disinformation is greater than the danger of the misinformation itself. Such industries have a vested interest in considering leftwing economic views to be disinformation, for example.
not to mention these companies have in many cases censored various accounts supportive of the Palestinian cause as antisemitic hate speech. The idea that these companies can be expected to police for anything but their own economic interests, as opposed to political principles we've no reasons to expect they believe in much less would place over their bottom line is pretty laughable. As a matter of fact whenever someone says a private company should get to police itself, that's usually a dog whistle for "they should get to do whatever they want, because I think they'll do what I happen to want them to do."
---the late great Donald Blake