I was a child in the 60s and a teenager in the 70s. I suspect a lot of you are younger than that. Back in the 70s there was a feeling that up to the 60s there were clearly understood rules and laws which had often been oppressive to women and young people. There was immense hypocrisy, as it was openly understood that lots of these rules/laws were broken with impunity by the rich and powerful.
For example, a young unmarried woman from a wealthy family who became pregnant and couldn't marry the father (or where the family were desperate for her not to marry the father) would be pressured into having an abortion. Abortion was illegal, but there would be no risk of prosecution as the family would know which strings to pull to ensure that the authorities turned a blind eye. Poor women and those who carried out their illegal abortions were at far higher risk of prosecution.
In the 60s and early 70s there was massive social change and one consequence of that was a fairly widespread feeling that there were no longer any rules and that everybody would find their own way through. There was a feeling in some quarters that children were an oppressed minority who should be free to do what they liked. For these people, the age of consent was not seen as a protection for young people but as one of the archaic rules that had always been widely broken and therefore ought to be scrapped.
There was also very little grasp that giving one group of people freedom to do whatever they liked might be problematic to other groups. Many men were absolutely delighted that it was so easy to find women for sex outside marriage but there was far less talk about the social pressure on women to comply with men's demands or be written off as frigid. Date rape and was not taken seriously, as we all know. Groping of women was so commonplace as to be completely unremarkable.
It's against the background of the complete confusion of the times that I recall there was some tentative public discussion about whether children had a right to engage in sexual activity. I remember vividly hearing a representative of the PIE on a mainstream BBC radio news programme (Today?) putting this forward as a libertarian stance. That was probably in the early 80s. It wasn't for a few more years that it started to become commonplace to hear news reports about sexual abuse of children. I remember how shocking it was to hear this talked about at first, and how hard to believe for those of us who'd been lucky enough to know nothing about this firsthand growing up. From that point on, the PIE was persona non grata on the news and there was no more talk about children's rights to sexual freedom. It was finally understood that this was actually about giving a free pass to people who were sexually aroused by children and young teenagers, regardless of the damage it might do to them.
I haven't read the Mail report this week, but this is not news. I think I read about it in Private Eye decades ago. No political parties come out of this kind of thing well, because judged by current standards they were all lacking.