Newspaper columnist and author H. L. Mencken (1880-1956) disliked The New Criticism: A Lecture Delivered at Columbia University, March 9, 1910 (1911)  by Joel Elias Spingarn (1876-1939). Mencken wrote in 1919:
 
“But what is the anarchist ex-professor’s own theory?—for a professor must have a theory, as a dog must have fleas.”
 
“A professor must have a theory, as a dog must have fleas” is a classic Mencken quotation that is still known by many college professors.
 
 
Wikipedia: H. L. Mencken
Henry Louis “H. L.” Mencken (September 12, 1880 – January 29, 1956) was an American journalist, essayist, magazine editor, satirist, critic of American life and culture, and scholar of American English. Known as the “Sage of Baltimore”, he is regarded as one of the most influential American writers and prose stylists of the first half of the twentieth century. Many of his books remain in print.
 
Google Books
Prejudices:
First Series
By Henry Louis Mencken
New York, NY: Alfred A. Knopf
1919
Pg. 12:
But what is the anarchist ex-professor’s own theory?—for a professor must have a theory, as a dog must have fleas.
 
Google Books
Last Minute Speeches and Toasts
By Andrew Frothingham
Franklin Lakes, NJ : Career Press
2001
Pg. 137:
“A professor must have a theory as a dog must have fleas.” — H. L. Mencken
   
Google Books
Cosmopolitan Vistas:
American Regionalism and Literary Value
By Tom Lutz
Ithaca, NY: Cornell University Press
2004
Pg. 40:
When Mencken, in inimitable style, attacked J. E. Spingarn’s nascent new critical theory in 1919, he did not blame him for having a theory, “for a professor must have a theory, as a dog must have fleas,” but for a particular kind of overreaching.
   
Salon
Thursday, Mar 8, 2007 07:52 AM EST
Think you know how to read, do you? 
A new throng of authors wants to save literature from our nefarious English departments and teach us how to read their way. Now, class, pay attention.
By Tom Lutz
(...)
It’s worth noting that the New Criticism was in its own day the new kid on the block, and it was seen as a fairly outlandish, ridiculously over-theorized assault on civilized reading. It is J.E. Spingarn’s 1911 “The New Criticism” that H.L. Mencken lampoons in “Criticism of Criticism of Criticism,” suggesting that Spingarn has a theory simply because “a professor must have a theory, as a dog must have fleas.”