It's the "anything can be a slur is you say it with enough hate" thing. You're just giving a name to the group targeted by it. The content isn't the thing that matters, it's the dehumanization and harassment.
From adults, yes
In other words, unless you believe Facebook is part of State or acts on behalf of the State, “you don’t get to shut down hate speech” is mereley your sentiment, not something Constitution requires from them.
If Mark Z actually called hate speech “protected speech”, it is something he is free to do, but Facebook is also completely free to suppress hate speech.
* https://www.nyclu.org/commentary/column-applying-constitutio...
"Billionaire oligarchs" only became a problem when a few of them became neutral or moderately right-wing.