It is interesting that Rosen expressly denies any connection between his subject, rockism, and l'affaire Merritt. (He calls it "another ball of wax.") In fact, the rockism debate (like any attempt to think categorically about American popular music) can't be extricated from ideas about race. One of the peculiar facts about rockism is that every generation of rockists disdains most contemporary black music but admires the black music of the previous generation. So '60s rock fans learned guitar licks from Robert Johnson and Hubert Sumlin but dismissed the Motown Sound as disposable teen pop. (They made room for Hendrix, who they managed to categorize as musically white [details here], and began to tolerate Stevie Wonder and Marvin Gaye once those soul men came around to rock-derived "concept album" forms toward the end of the decade.) Today's rockists are OK with "Dancing in the Streets" but not "Ignition (Remix)." (Everybody likes "Hey Ya!")
Kelefa Sanneh described the famous 1979 anti-disco rally at Comiskey Park as "the Boston Tea Party of rockism." The image of thousands of white Chicagoans burning records made largely by blacks and gays makes it obvious that the word rockism exists in part to connect anti-pop fervour with uglier and more consequential forms of prejudice. That's why, when music critics accuse one another of rockism, they're not smiling: there is a moral dimension to the accusation, one that winds together aesthetics and race politics.
(Merritt, of course, is none of these kinds of rockist. In a 1995 interview, he said "Rock should have consisted of only the Paul McCartney branch, not the Lennon/Jagger/Richards one," which is a more doctrinaire statement of reflexive antirockism than you'll hear from SFJ on a bad hair day.)
Really, I think the SFJ/Hopper case against Merritt falls down on a confusion of the proper roles of critic and artist. A critic who disregards entire important swathes of his/her chosen field exposes him/herself to charges of narrowmindedness. An artist who does the same thing is just engaging in some necessary clear-cutting. Merritt, I think, is a full-time artist and a dilettante critic, and that's what gets him in trouble.