A couple of things:
Yes, there's no doubt that the white guys in the South seeking James Brown in a Blacks-only Motel were more death-defying than the little girls were, going to a Beatles concert. But the Beatles were NOT "clean cut English guys wearing suits" to the older generation-- they were androgynous foreigners. Very threatening, at the time. By and large, parents in the U.S. wanted their sons to have crewcuts, marry their prom date, and enlist in the army. And they did not want their daughters to consider a man with hair longer than a crewcut and no U.S. birth certificate.
Your Marilyn Manson observation made me think about my opinion of Kiss. I would consider them "rock" (they ain't Celine Dion), but their schtick has such a cheesy, bubblegum quality to me that I've always felt that they were on the edge of "pop" music. For example, the late British singer-songwriter Nick Drake sang almost in a whisper and played acoustic guitar, but his emotional impact and artistic integrity make him more "rock" than Kiss would ever be, to me.