FORTUNE — This Saturday, Amazon will give a 5% discount, up to $5, to people who scan prices at a physical store into its Amazon Price Check mobile app, then buy the items online. Predictably, this has stirred anger and disgust. Those emotions are woefully misdirected.

“Local shops” are the victims in the accounts of Gawker and others, including lots of people on Facebook and Twitter. “Apparently concerned that it’s not already doing enough to undermine local physical retailers across the country,” according to Gawler’s Ryan Tate, Amazon will give customers the discount on select items. “Please don’t do this cheap, sad thing,” he writes.

Lower down in the item, Tate provides a caveat: “By all means use Amazon — they have amazing selection! — but there’s no need to be a tacky jerk to your neighborhood store in the process. Unless that store is a Wal Mart (WMT), Target (TGT), or American Apparel (APP), in which case, go to town (by which we mean, go out of town).”

But the “neighborhood store” almost certainly is one of those stores, if it’s not Best Buy (BBY), Barnes and Noble (BKS), Home Depot (HD), or some other retail oligopolist. And anyway, Amazon’s “amazing selection” (along with its top-tier customer service, speed of shipping and  low prices) is the real, ongoing threat to physical stores. So why is it ever OK to shop through Amazon?

Often when Amazon is the target of such rage, the supposed victim is theoretical — the mom-and-pop shopkeep; Bob and Sons Nails and Flour; the local electronics store with the wildly inflated prices and shifty salesmen.

But those kinds of stores were mostly obliterated years ago by — yes, Wal-Mart, Target and the rest. Amazon (in this instance, anyway) is the renegade upstart striking a blow against the big, evil monoliths. No doubt some independent, locally owned stores will take some incidental hits. But if such promotions are going to truly hurt those businesses, they’re in trouble anyway — probably thanks much more to Wal-Mart and Target than to Amazon. And those giant stores are much more likely than local shops to have the bar codes needed for the app to work.

Also, since when — regardless of the perceived morality or market power of the retailers involved — is comparison-shopping a bad thing? A “cheap, sad” thing?” Lecturing shoppers on their price-based decisions in a weak economy is a particularly obnoxious display of arrogance. If some unemployed father is, thanks to this, able to get his kid the Gummy Bear lamp she’s been yearning for all year, I say Merry Christmas to all except for the people who would call him a “tacky jerk” for doing so.