So basically Facebook is like, you and you, fight! Also buy our weapons.
(generally speaking, people rush to buy guns whenever the specter of gun control comes up, because they think that'll be the last chance they get.)
And it's mostly in their head. The right was fired up for eight long years driving up the price of guns and ammo while Obama was president, meanwhile he never made even a token effort at gun control.
That's not actually true, there are incidents like the ammo import ban to automatically prohibiting elderly people receiving financial assistance.
The fact that the gun control you were expecting didn't happen doesn't mean that none did.