Meanwhile, having no kind of registry of firearms[1] is the very epitome of utopian perfection?
But I get it. Some people just don't want to be 'tracked' by dat ebul gubmint, and cases such as the above is just one of the lesser of all paranoid-looking arguments.
(Honestly, if someone achieved their ambition and used their stache of weaponry to actually overthrow the federal authorities, in a mass "power to the people!" episode, I doubt any significant proportion of bullet-striations/whatever will get checked against recent barrel-records to see if they can establish which particular insurectionist had failed to swap out the relevent components between "the ones used in the mandated test-firings" and those saved against the day of the mass uprising.)
As said by others, data-protection is a general issue. If this was an over-reach of released information, by an individual, it's probably no more a problem in the long term.than a major online retailer's purchaser information getting exposed (less so, in at least some rsspects). Or that recent loss of the USB stick in Japan (encrypted, apparently, but I don't know to what degree of sucficiency) that had pretty much an entire city's detailed resident information upon it, should anyone find and be able to make use of it.
Sorry, no, if there's a 'pile' of bad reasons for firearm (and/or firearm owner) database, I suspect that the pile of good reasons is also significant. And possibly contains some of those things from the first pile but just from a different reasonae perspective, indicating nuances in their pro-/anti- application at the very least.
[1] Though this is firearms owners, isn't it? You need to be able to check that someone with a firearm is allowed/not disalloweddelete as inapplicable to carry a gun. The secondary aspect of exactly which (or indeed how many) weapons they possess is another question. But, again, it wouldn't hurt to have the permanent serial number, and perhaps a ballistics fingerprint, on record for every gun (linked to the nominal owner by a pseudorandom anonymisation tag on both databases that requires legally-authorised cross-checking) to allow everything from returning stolen and recovered guns to get back to their owners all the way to at least bootstrapping the investigation of where a weapon was involved in a crime, whether that be a direct lead or the start of an underworld trail starting at someone having let an unsecured weapon get stolen in some random robbery.