It'd be easier to take moral panics even a little bit seriously if one actually turned out to be true.

Has there ever been a moral panic that turned out to be true? The closest I can think of is maybe the teetotaler/prohibition movement. Alcohol truly does cause a great deal of harm to society.

Not having been alive in the late 1800s and early 1900s I can't speak to if it was really viewed as a moral panic similar to the Satanic Panic of the 1980s that I got to experience.