Separate question, though - that's particular kinds of material (and for some reason US caselaw basically doesn't regard anything pornographic as "speech"), while this is a blanket restriction.
The list goes on and on.
I fail to see how not being allowed on Facebook is different.
Social media companies aren’t required to give a voice to anyone. They are platforms for enabling exercising speech, but they aren’t speech themselves. This seems equivalent to stating that not allowing children in bars or strip clubs violates their right to assembly.
As far as I'm concerned, this Florida state law practically extends it to children age 16 and under specifically with regards to social media websites and services.
[1]: https://en.wikipedia.org/wiki/Children's_Online_Privacy_Prot...
[2]: https://www.ecfr.gov/current/title-16/chapter-I/subchapter-C...