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.