I recently bought a stack of ACG (American Comics Group) comics from the mid-1960s. I was surprised, though perhaps shouldn't have been, that, within the letters columns of a few titles, raged a long-running debate about the presence of -- and the merit of -- superheroes, especially in what many readers believed should be strictly mystery or supernatural titles. A few letter writers even expressed extreme hostility to such heroes (one signed his letter only "Costume Hater"). At the link above, Don Markstein says that "reader demand [for superheroes] was incessant, and in 1965 he [Richard Hughes, ACG editor/writer] finally gave in. Adventures into the Unknown launched Nemesis and Forbidden Worlds launched Magicman. Hughes's lack of enthusiasm for the long-underwear guys was reflected in the readers' lack of interest in them."
If the letters I have read are any indication, while many readers wanted only horror or fantasy, many readers were deeply invested in "costume characters" and were happy to see them in ACG titles. And, at least in his public role as editor on the letters pages, Hughes often expressed enthusiasm for the "supernatural superhero" that appeared in his comics, which he might have created as a way to appease the demand of both camps of readers. As he notes in AIU 173 below, however, ACG decided, from that point on, to concentrate on supernatural and fantasy stories, not superheroes. [There is a history of ACG that perhaps answers questions about Hughes's personal beliefs.]
Although many letters do not deal with the issue of "costume heroes," I have scanned each column in full because there are other things of interest in them (especially fan and editorial discussions of ACG artists like Ogden Whitney, Chic Stone [and his work with Jack Kirby], Pete Constanza, and others). It's also interesting to read these fan letters because their approach to reading, criticism, and interpretation is often so different from mine -- the readers often focus on questions of science, consistency, believability, and adherence to genre and marketing conventions. [Click and on each image, then click again to enlarge.]
Adventures into the Unknown #162 (1965)
From Unknown Worlds #46 (1966):
Adventures into the Unknown #163 (1966):
Adventures into the Unknown #165 (1966):
Adventures into the Unknown #173 (1967):
