It's understandable that Microsoft would be testy about their unintentional Vista easter egg. Whether it's good PR to take it out on your customers like this is questionable, however. I seriously doubt that people who are taking advantage of the upgrade loophole aren't aware that they're cheating. But the reason that it's Microsoft's head of the VAR program who's leading the scold-a-thon is that it's probably small Value Added Resellers who are taking advantage of the loophole to install Vista licenses on machines for their clients without having to pay.
It's easy to see the temptation. The client gets a fully valid Vista license, the VAR gets paid, but only pays half the license fee, and everyone's happy except Microsoft. Certainly it's easier to morally justify taking an unauthorized discount off the Vista license fee than out and out pirating it. Many people will air their grievances about Vista's quality or Microsoft's past licensing transgressions while they stick it to the man, and feel justified.
One big question this issue raises is this: is the accidental half-off program pushing anyone to buy a half-legit Vista license who would otherwise wait it out or pirate it? Or is each of these phony upgrades just a out-and-out revenue loss for Microsoft? Are the cheaters in any way justified? Or is paying half for an "illegal" install just as morally wrong as installing a pirated copy?