As soon as we add one asterisk to free speech other people will want to add to the list.
That's how we got runaway 'hate crime' and 'hate speech' laws.
And if Zuckerberg gives in (which he will) the SPLC and the ADL will decide what else needs to be banned.
This may be an unpopular opinion but if we are to keep our right of free speech, we have to allow Holocaust deniers to say what they want.
But I revere free speech and have no problem with holocaust deniers having the right to speak or publish about their beliefs.
I was raised that our country is so free we are to let Nazis and KKK have their marches, Voice their opinions, and let Good ideas win naturally over Evil ones. Im ok with it.
(And I still think Zuck is an a hole even if we agree on this small point.)