What you’ve charted is the loss of "innocence" in mainstream American media. It is tempting to use that to extrapolate historical trends, as you have, but it is hardly a accurate historical barometer. The changes in media have more to do with what was going on in the media (the Hays Code, movie ratings, the FCC, etc.) than in the lives of people.

Yeah, I want to live in the 1920s too, but not because of the "innocence" of the time, but because it was actually a pretty wild time, with gangsters and flappers and free-flowing gin and jazz and Cole Porter. Don’t use a silent movie to judge the character of the time; look at what actually happened.

Or better yet, go back a few centuries. In Shakespeare, characters are forming "the beast with two backs." Read the raunchy tales of Boccacio’s Decameron, with its frolicking nuns and monks and priests. Then try to tell me that the past is more innocent than today.