What to say when you see something so monumentally wrong that it makes words disappear from your vocabulary!! That’s where I am at after reading your post. The problem you are facing, and I don’t even believe it is a problem because I supported the Red Hat guy, is that there was much more incorrect information posted about Trump than there was about Clinton. And much of the incorrect stuff was horribly damaging to him and probably will continue to damage him and by reflection our country for at least 4 years and probably 8.
Take the comments about Trump being anti-Mexican. Remember the quote saying “they’re rapists”? He (Trump) never said that. What he said was “their rapists” when discussing who was coming across the southern border without passing through the screening process. The difference between They are rapists and their rapists in this context is huge.
I think you should be demanding that incorrect items for either side be immediately and retroactively found and an opposition notice be pasted on the offending page and everyplace it was displayed. I don’t like the idea of anybody editing or deleting anybodies post, but putting up a retraction or automated incorrect information flag would certainly be acceptable.
On balance I would say that overall facebook brought more votes to Hillary than they did to Trump. Thus even if they do nothing you have no standing to complain.