Let's be clear here. You have the right to spout off in the public square without government consequences. Others, including Meta itself, are still free to hold you accountable for what you say.
It seems like the OP might have been conflating free speech with admissions of guilt for other crimes, but "spouting off" is not, and must never be, a crime.
By my reading, it wasn’t OP who did this conflating.
"spouting off..used against you in a court of law"
But, even if the OP didn't intend for these two to be tied together in this way, then a very strong constitutional right still exists for spouting off, so whether conflation occurred or not is moot.