Philosophy Discussion Question

Our textbook author, Robert Paul Wolff, claims that Kant "liked to say that his Categorical Imperative was nothing more than a philosophically more precise statement of the old Golden Rule: Do unto others as your would have others do unto you….Kant thought [the Categorical Imperative] contained the same basic notion" (pp. 154-155, About Philosophy). However, there is reason to deny what Wolff says here. Here is what Kant actually says in a footnote in hisGroundwork of the Metaphysics of Morals: "Don’t think that the banal ‘Don’t do to anyone else what you wouldn’t want done to you’ could serve here as a guide or principle. It is only a consequence of the real principle, and a restricted and limited consequence at that. It can’t as it stands be a universal law, because it doesn’t provide a basis for duties to oneself, or benevolent duties to others (for many a man would gladly consent to not receiving benefits from others if that would let him off from showing benevolence to them!), or duties to mete out just punishments to others (for the criminal would argue on this ground against the judge who sentences him). And so on." So it seems that Kant did NOT think that the Categorical Imperative was simply another version of the Golden Rule. 

Explain why Kant rejects the idea that not doing to anyone else what you don't want done to you falls far short of being a universal moral guide or principle. Why, according to Kant, should a rational moral agent prefer the Categorical Imperative to the Golden Rule?