Say it were implemented in this world and you could say anything you like (written, spoken, signed whatever) to anyone who can hear/read/see it. What kind of problems could that create and are there any ways to resolve them without limiting that absolute free speech?
Could it even create unsolvable logical errors? E.g an omnipotent god can’t create a stone too heavy for itself to lift. Maybe there are similar things with absolute free speech.
The point is that the planning itself wouldn’t be illegal if there were absolute free speech. Of course the murder still would be, but ideally you’d want to stop that before it happens, which will be tougher when just talking about murdering people is perfectly legal. Free speech isn’t just about “naughty words”.