I'm removing about.com as a link on my blog - I liked it better when it was run by Mike Moffatt.
Whether or not students were 'right' to walk out of class is beside the point - the point it seems that Ms. Beggs can't see. Value judgement are inescapable in the economics of real life. Half of the so-called 'positive statements' in economics are really just normative statements disguised by bad and unrealistic assumptions.
I agree the students don't quite perhaps articulate their own beef very well, but the point about Adam Smith vs. Keynes, as I read it, was more to point out the broad fact that Mankiw teaches a specific ideology, at the expense of alternatives - not just Keynes'. And the Keynesianism he does teach is arguably not the Keyensianism that Keynes would have taught himself. (See distinction between Post-Keynesian economics and so-called New-Keynesian economics).
And now for my shameless plug: anti-mankiw