FB says it would be a violation of free speech to block doctored videos, like the bogus onepurportedly showing Nancy Pelosi slurring her speech. The way to get FB to eliminate all such tricks is to have FB posters in the thousands do the same to Trump videos. Then FB will be forced to re-think that so-called free speech policy.
The left already makes such doctored videos about Republican candidates. They are only squealing now because the Republicans are giving them a dose of their own medicine.
It is highly unlikely that Facebook would have any objections to unfair attacks against Republicans. They have a clear leftist agenda.