there were loads of songs from say the 50s onwards that actively expressed sexual fantasies around young women, pondering 'are you sixteen?' and so on. There was a definite fetishisation over teenage girls that seems to be have been a cultural meme even...and it was reinforced by men across the media, on tv, in the papers, and the less said about djs the better.
Whats upsetting to me about older men sleeping with young teenagers is the more than likely power imbalance - which suggests a degree of coercision and taking advantage, but also that the older man is getting a power trip from the whole experience. The power tripping also feeds into the way men were talking about it in the media - men ran the media in those days in a way they don't exclusively do so as much now. I'd like to think that sexual power tripping culture amongst men has changed somewhat since then, not just acting differently because it would be disapproved to sleep with young teens.