I think there was an effort by some progressive gays to infiltrate and use the Church for their own agenda.
These same groups attack Church doctrine in other areas as well.
BTW, I'm not convinced that homosexuality was as
big a component as he thinks. It could very well be
that sex with boys wasn't about a homosexual
orientation, but just a way to have sex & human
contact of any kind. In such a case, it would be
a perversion, not homosexuality.
It's common to try and equate homosexuality with clergy's abuse of children. However, both male and female minors have been abused by clergy, it's just that the majority of victims are male. This makes sense when you think about their access to children, as altar boys have always been the norm. The Vatican only allowed for altar girls in the mid-1990s. When you consider how many decades (centuries, no doubt) this abuse dates back, it's clear this is a contributing factor of convenience.
It's not solely a matter of homosexuality nor even primarily so, and arguably not at all in various cases. If it was simply about homosexuality the priests could satisfy themselves with each other instead of diddling kids and no one would be the wiser. This is primarily hebephilia (abuse of pubescent children) and ephebophilia (abuse of teens) and some pedophilia (prepubescent). This involves the desire to have power over a sexual victim and, certainly, in decades past, this was easy to achieve. It was the norm to never question a priest, they were assumed above reproach. Adults would believe "a man of the cloth" over a child's protestations, which only embolden them.