I do not agree with the OP's apparent presupposition that age somehow invalidates truth (without even giving us so much as an alternative and a basis for accept

I do not agree with the OP's apparent presupposition that age somehow invalidates truth (without even giving us so much as an alternative and a basis for accepting it). However, the law is incomprehensible without morality. What on earth could you possibly take the law to be in the absence of morality? The natural law is the basis of morality and morality is the basis of law which is the particular and concrete determination of it in especially in matters concerning the common good. Yes, there is such a thing as immoral speech. Slander is an obvious example. Lies. But what should be subject to the law? That is a prudential question. And the 1st amendment is interpreted to some extent according to more or less prudential considerations.