Who Were the Sea Peoples?

So, John McWhorter gives the usual linguists' argument against prescriptivism in this lecture course : languages always change, there is no such thing as perfect language, today's standard talk was yesterday's mistakes, no recorded language has ever fallen apart into nonsense, and so on. By and large, I agree with this case. However, McWhorter seriously overstates it when he claims that correcting a child's grammar is "just like" smacking the kid in the back of the head and ordering her to color within the lines in her coloring book. First of all, unless you physically punish the child for bad grammar the analogy is rather outrageous hyperbole. But more importantly: Just as languages always change and today's mistakes become tomorrow's standard speech, haven't adults always corrected kids' speech? In fact, couldn't this be an important aspect of the very process that keeps language from changing so fast that people only two or three gen...