To be clear. The Constitution puts limits on the government. The 1st Amendment limits what the government can do regarding limiting free speach.
"Congress shall make no law…."
Maybe anti-monopoly laws would be another tactic. That is the issue really, FB, G**Gle, TW and YT have basically monopolized their respective areas giving no other venue for ideas they don't agree with. The 1st amendment doesn't really apply to private entities (as far as i know). Full disclosure - I am obviously not a lawyerfag so I may be full of shit.