There's legal recourse for this (see Chaplinsky v. New Hampshire, among the many other SCOTUS rulings curbing free speech in special cases). Social media companies are not the arbiter, the courts are.

Fighting words only apply to face-to-face speech and even then it's somewhat doubtful. If you want further analysis, look at some of Ken White's writings on it on Popehat. Incitement as defined by the Brandenburg test is more likely to apply.

I dont expect FB to be a arbiter, but in a more general sense, prevent harm done using the facility. Like a transport company to be held liable if someone is using them to mule drugs, or banks for money laundering.

If we're using the word "attack" to refer to a legal action, I think that is something that is very important for voters to be aware of.

Not legally, sticks and stones.

Then the speech is illegal and not an example of a reason the dichotomy would be false.

Calling for violence is illegal in The Netherlands if I recall correctly.

They should stop anyone who fails the Brandenburg test for incitement, but that's already illegal.

You can make a coherent argument that they shouldn't, but that would require much heavier censorship on Facebook's part than is present today. How many Facebook posts glorifying the looting were left up uncontroversially?