Time's weren't that different. It was sickening then, too.
But the Press said it was alright. Men said it was alright.
Same reason why Jimmy Page got away with abusing Lori Maddox (who, in an interview, said 'I was still a -' and hastily stopped herself from saying 'virgin', correcting it to 'a baby'.
Because they were men that other men wanted to be like.
My old optician was chatting about attitudes during my eyetest a few years back, well before Yewtree (he was a great guy, was a musician as well as a student in the late 60s/70s - we had some great conversations between 'better like this? Or like this?') and he also said that there was a HUGE fuss about naked children on album covers, but the power of particular bands/management/record labels meant that it was normalised, along with the underage groupie image.
Suppose if they could normalise the use of images, it would create an atmosphere where abusing children was seen as an aspirational thing, part of the Rock & Roll Lifestyle.