I think that some people, especially religious fundamentalists, think rock n'roll is the devil's music because they thought that's what makes teens sexually aroused, addicted, violent, anti-social, or just plain wild.
If they can tell that rock music has something to do with the devil, they either listen to the music for any lyrics related to immoral behavior or play it backwards to find any "hidden" satanic or drug-related messages. Example: If you play The Eagles' "Hotel California" in reverse you'll hear references to Satan. Also, reverse Queen's "Another One Bites The Dust" and listen to "It's fun to smoke marijuana" in the chorus.
Some people charge that any type of rock music sometimes promote death. Emo music, for example, promotes self-harm in their lyrics and has lead to reports of teenage suicides.
It's ridiculous to hear that, as what you said, KISS (allegedly) stood or "Knights In Satan's Service". Rock stars may be accused by concerned parents or religious leaders, but they would still make music and attract fans. And don't forget: most rock music doesn't promote immoral behavior and is sometimes toned down by some music promoters.