And if you worry that I'm using a primary source here, this quote was noted in a review of Rocker's book by a Yale professor, who said that: "Rocker's conclusions concerning American radicalism is the most interesting part of his book. Pointing out the universal and inevitable movement of cultural influences back and forth among nations, he indicts the stupidity of the "one hundred per cent Americans" who distort the importance of such streams of influence and label radicalism as a foreign importation." Then he quotes Rocker, which quote I already provided somewhere above here.