You realize, of course, that guns which became NFA Title II in the past were all allowed to be registered tax-exempt? This blogger has nothing to base his claims of a taxation aspect on besides his own speculation.
And, the pie-in-the-sky plan to make AR-15s and/or other "military style auto-loaders" fall under Title II and be registered has about a snowball's chance in hell of passing into law. Forcing registration of approximately 50,000,000 firearms -- but who knows really how many? -- would just about grind the fed.gov to a halt. The ATF is processing about 105,000 Title II registrations a year right now and it takes them 6 months + to get each one done. So, register all semi-auto rifles of the most common type? Yeah...THAT'S
238 YEARS WORTH of registrations they'd have to swallow. You can expect your registration papers back in the year 2251. And they can't nail you for it if they haven't gotten around to processing the paperwork on your "grandfathered" registration...
Still think this is going to happen?
Now look at Canada and their firearms registration law. It was so comprehensively IGNORED throughout most of the country that it became an absolute joke. Unenforced and unenforcable, it eventually was retracted as it showed the government to be utterly too weak to enforce the laws it had passed. The US Congress will not risk passing a law that the citizens have the physical ability ... in fact, almost utter certainty ... of ignoring and refusing to comply with, with near certain immunity.