No, it's not jailed for facebook post, it's jailed for a facebook post calling to an immediate specific violent action against a specific person. If a mafia boss tells his capo "let's whack that mofo", then it'd be very disingenuous to claim the mafia boss was prosecuted for speech, not for organizing a murder. Obviously, free speech protections do not apply when the speech is a part of a crime - either one that happened or one that is about to happen. Saying "let's burn this specific guy's house down" is well within the limits that should get police's attention.

Even then, in this case, Peralta was not prosecuted. Which is probably OK if he was just extremely stupid and not actually intended to proceed with burning the house down. But specific violent threat is not the same as just speech, and one should never present it as such.

You read his comment right? He publicly posted "...It's time to strike back. Let’s burn this motherfucker’s house down." About a police officer. It is not right to post that.