Prescreening would massively damper speech to make it essentially Cable TV while not even solving the issue of PTSD as there would still be screeners. That isn't a solution - it is misguided spite.
Second it is the price of a remotely free society - not having to ask of freedom of speech - letting the government decide what is "unacceptable for society" with speech is foregone conclusion of abuse. Besides even if it was miraculously representative society doesn't even know what is good for society! The Romans thought that their gladiatorial games were opposing decadence and that wearing pants was barbaric and worse for society than putting lead in wine.
Second it is the price of a remotely free society - not having to ask of freedom of speech - letting the government decide what is "unacceptable for society" with speech is foregone conclusion of abuse. Besides even if it was miraculously representative society doesn't even know what is good for society! The Romans thought that their gladiatorial games were opposing decadence and that wearing pants was barbaric and worse for society than putting lead in wine.