This is a completely evil proposal from a libertarian perspective.
As Murray Rothbard observed:
The consumption tax...can only be regarded as a payment for permission-to-live. It implies that a man will not be allowed to advance or even sustain his own life unless he pays, off the top, a fee to the State for permission to do so. The consumption tax does not strike me, in its philosophical implications, as one whit more noble, or less presumptuous, than the income tax.
Further, Johnson likely means the horrific VAT when he talks "consumption" tax.
Johnson is simply an opportunist. Rothbard wrote many years ago when discussing libertarian strategy:
In the name of practicality, the opportunist not only loses anyBottom line: No self-respecting true libertarian would ever advocate any form of consumption tax.
chance of advancing others toward the ultimate goal, but he himself
gradually loses sight of that goal—as happens with any “sellout” of
principle. Thus, suppose that one is writing about taxation. It is not
incumbent on the libertarian to always proclaim his full “anarchist”
position in whatever he writes; but it is incumbent upon him in no
way to praise taxation or condone it; he should simply leave this
perhaps glaring vacuum, and wait for the eager reader to begin to
question and perhaps come to you for further enlightenment. But
if the libertarian says, “Of course, some taxes must be levied,” or
something of the sort, he has betrayed the cause.