… is from page 125 of the 1997 Johns Hopkins University Press edition of H.L. Mencken’s 1956 collection, Minority Report :
The only way that democracy can be made bearable is by developing and cherishing a class of men sufficiently honest and disinterested to challenge the prevailing quacks. No such class has ever appeared in strength in the United States. Thus the business of harassing the quacks devolves upon the newspapers. When they fail in their duty, which is usually, we are at the quacks’ mercy.