Their book, JFK and the Reagan Revolution, released in September 2016, makes the point well, as does this article in Forbes:
And sure enough, with the income tax presenting itself as patriotically taxing the rich—at times with utterly fictional 91 and 94% top rates, from the 1940s until the 1960s, as Larry Kudlow and I marvel at in our recent book, JFK and the Reagan Revolution—government was able to grow where government under the tariff could not. The income tax supervised the rise of the federal government to well over a fifth of national output—from 3% during the era of the tariff. ... The dishonesty at the heart of the income tax was the key that unlocked the financing of big government, by the little guy no less.
We've been making the same point, more or less, since at least 2011, and especially in March 2016 here:
[Mark Levin's] tariff rant this evening ignores that the America of his precious founders was a tariff regime until the dreaded income tax of 1913.
The America of the founders was also a limited government for that reason until that very day.
But open wide the avenue for revenue, and you open the maw of the Leviathan and crawl into it.