Really, the thing is that the whole "single tax idea" is a bit misguided. A consumption tax (sales tax) is great, but there are some sensible reasons to tax capital income/investment to
some extent, too. Mostly, because it correlates somewhat with basic ability-to-pay; also, because people might try to disguise income/expenses as investment-related in order to shield them from taxation, and having a more uniform tax base helps prevent this.
But the broad principle that capital investment should bear a lower tax burden is quite correct. And one you've accepted that general principle, it makes a lot of sense to tax rent-generating assets like land and spectrum rights (since those are not really "capital" in the first place), which is pretty much the Georgist idea.
