George Weigel traces it to a series of articles covering Vatican Council II, some fifty years ago, which happened to dovetail nicely (as it still does) with the way postmodern society looks at the world:
In a culture in which people imagine that religious conviction is a lifestyle choice of no more intellectual or moral consequence than the choice of a pet, it takes serious effort to grasp that what the Catholic Church teaches about the nature of God or the requisites for ministerial ordination is entirely different from the choice between a schnauzer and a dachshund. And in a secularized culture in which “choice” is the one sacred word, a Church that insists that its leadership teaches authoritatively is going to be easily portrayed as ham-handed, insensitive, out of step.Read the whole article here. It's worth your time. And I'm not just saying that because it says many of the same things I've said in these pages.