There was certainly a culture of consenting sex with minors (15,16 17 year olds for example) > However, sex with (or molestation of in the case of thornley) was not a commonly held philosophy. There has been a lot of debate on Bey's writings, was he making a philosophical argument from a "no one should tell someone else who they can have sex with" position, or was he personally interested in sex with prepubescent children? It simply cannot be stated with certainty. There is even some evidence that Hunter Thompson may have had leanings toward pedophilia, but again, so concrete evidence.
On the topic of Thornley, though, its extremely likely that at least once he did engage in molestation of his young niece. The other people present in the house (also hippie/leftist/liberals) were NOT OK with his behavior and forced him to come out of the room where he was alone with the child. Its also worth pointing out that by that point in his life, he was showing signs of serious mental disorders. That doesn't excuse any behavior, but it does put it in a different context than a"tolerant culture".