In Defense of the Phrase: "I Could Care Less"

I seem to be fighting a losing battle in attempting to explain why the phrase "I could care less" is perfectly correct English grammar in the context in which it is normally used. Here's how I see it. When someone uses this phrase, we know from common sense exactly what this person means -- namely, that this person doesn't give a whit about whatever is being discussed. So, using this clear meaning as the baseline for figuring out the grammar, the next question should not be whether the grammar is correct, but actually how the phrase represents correct grammar. And how it's correct is by recognizing it as the elliptical clause that it actually is. An elliptical clause is one in which some words have been left out of the clause, but the meaning of the clause is clear enough by its logic, in spite of such word omissions, in order to be able to discern what the missing words are. Thus, when someone says "I could care less," what he is clearly saying, and what everyone knows him to be saying, is essentially "(As if) I could care less (than I already do, which is not at all)," or simply "(As if) I could care less."