A recent (2014) political scandal in the UK shone some unflattering light on the situation here from the late 1970s to the early 1980s, when an organisation called the Paedophile Information Exchange was allowed to join a major pressure group, the National Council for Civil Liberties (NCCL - now just Liberty), and campaign openly for the reduction in the British age of consent to four. For a time, the NCCL itself supported the lowering of the age of consent, to as low as 10 when both partners were aged under 14.
PIE became an NCCL affiliate group in 1975. At that time the term "paeodophile" was not in common use in the UK or even generally understood, which helps to explain the relative lack of reaction to its early activities. In addition, PIE claimed to be a "radical" organisation and successfully sought support from other radicals and from defenders of free speech. At its 1977 conference, the NCCL issued a strong defence of PIE against "hysterical and inaccurate" attacks in newspapers.
Broadly, PIE claimed to be a "campaigning and counselling organisation" that did "not promote unlawful acts", and made an effort to brand its activities as an effort to understand "children's sexuality". One PIE leaflet distributed to MPs suggested that “paedophiles are ordinary, decent, sensible human beings, no more sexually depraved than yourself, and with a capacity for loving and helping children which is at present being repressed.” In short – and according to Christian Wolmar, a journalist who covered the organisation at that time –
"They didn't emphasise that this was 50-year-old men wanting to have sex with five-year-olds. They presented it as the sexual liberation of children, that children should have the right to sex."
It has since been shown that at least seven PIE members received convictions for paedophilia during or after this period, and one was a major KGB spy. Another member turned out to be the Director for Education at the National Institute of Social Work.
It's fairly hard to go further without breaching the 20-year rule, as most of the detail and commentary appeared well after 1997, but broadly it appears that many members of the NCCL justified their support for PIE because they bracketed it with the gay rights groups who campaigned under their banner. This was a period in which there was still enormous prejudice against gays. Homosexual sex had only been legalised in 1967, and during the 1970s the age of consent was 16 for heterosexuals but still 21 for homosexuals – so pressure to reduce the age of consent for homosexual acts seemed legitimate to may liberals. When two of PIE's leaders were interviewed by The Guardian, a British left-wing daily, they expressed irritation that their aims did not receive more widespread support: "We would expect the Guardian, a decent liberal newspaper, to support us."
PIE did receive some support from other organisations. The main trade magazine for social workers, Community Care, published a feature in 1977 that argued for the “liberation of children to enjoy their natural sexuality” and informed readers that most paedophiles were attracted to children aged over 10, making them “less frightening than [PIE’s] campaign implies”. Andrew Lumsden, one of the editors of Gay News in the 70s, has said: “We were fighting against a lot of outmoded laws, and perhaps the ones against paedophilia were as outmoded as those against homosexuality or cannabis.” The Campaign for Homosexual Equality (CHE) twice passed motions condemning the "harassment" of PIE by journalists in the same period, and as late as 1981 Batsford, a mainstream publisher, published a book by a Sussex University academic titled Perspectives on Paedophilia which, according to its preface, aimed to "inhibit antipathy" towards both the discussion and the "indulgence" of paedophilia.
It took a series of criminal trials and exposés in the early 1980s to destroy PIE, which disbanded in 1984.
The issue became news again in 2014 because it became a party political issue. A former Labour cabinet minister, Patricia Hewitt, had been general secretary of the NCCL at the time that PIE was admitted to membership, and the then Labour deputy leader, Harriet Harman, was its legal officer. Particular outrage followed the discovery that Harman had written a letter to the Home Office in April 1978 arguing that child pornography should not be banned as “indecent” unless it could be shown that the child depicted had been harmed.
Hewitt subsequently issued an apology and described the NCCL of the 1970s as "naive" to have accepted PIE's claims to be nothing but a campaigning organisation at the time it sought membership. Matthew Parris, a gay former MP and current newspaper columnist, has suggested much of PIE's success was a product of the ignorance of those to whom it pitched its message: "If there was anything with the word 'liberation' in the name you were automatically in favour of it if you were young and cool in the 1970s. It seemed like PIE had slipped through the net."
All this should not be taken to show that there was general tolerance or acceptance of PIE's message even at the time. Spokesmen for the group were invited to speak by some student unions and professional bodies, but Parris remembers "a lot of indignation about it [PIE]. It was considered outrageous." Invitations extended to PIE's chairman Tom O'Carroll to speak at Liverpool and Oxford universities were cancelled after protests. A significant number of CHE members were also opposed to PIE.
I've searched for but not found significant coverage of this issue in academic sources, but I think it is important to give the references I have been using, which are mostly UK broadsheet newspapers.
Sources
BBC News, How did the pro-paedophile group PIE exist openly for 10 years?
Daily Telegraph 21 + 25 February 2014
The Guardian 27 Feb 2014
Related/follow-up question: did the Victorians think child sexual abuse was worse than now-accepted sexual practices that they considered immoral, like adultery or homosexuality? Or in the same league?
Didn't the Greeks and romans have man boy love relationships? I also believe there are tribes in New Guinea where young boys felate older men to gain their strength. It would seem that the stigma is not universal at the very least.