From a comment I put on StandFirm, which was later picked up by Anglican Mainstream:

In the late 1960’s the focus of Anglican theology  shifted dramatically — and so did the seminaries:

Liberal Protestantism (in the sense represented by Diocese of New Westminster, Canada, Bishop Michael Ingham) did not exist at all until Friedrich Schleiermacher, and did not exist in Anglicanism until the late nineteenth/early twentieth century.

Historic Broad Church Anglicanism was not Liberal Protestantism. (F.D. Maurice and William Temple, for example, believed every article of the creed.) Additionally, until the last twenty years or so, liberalism was never considered at the center of Anglican identity, but was tolerated as a kind of protest movement in the church with the understanding that Reformed catholic orthodoxy was the heart of Anglican identity. Anglican authority was defined by the sufficiency of Scripture, the creeds and the theological content of the (1662) BCP , as well as the 39 Articles, all understood fairly literally.

I have seen little evidence that “historic Broad Church Anglicanism” still exists. What used to be called “Broad Church” seems to have morphed into Liberal Protestantism. Perhaps it still exists in the C of E some place.

Wherever I have found acceptance of same sex-unions, I have also found theological compromise on other issues as well. In TEC these days, the dominant theology seems to be either blatant Liberal Protestantism or an “Affirming Catholicism” that is really “Unitarian Dress-up,” a love of “smells and bells” with minimal commitment to Catholic Theology.

Certainly the seminaries are largely responsible. If one reads the theological literature of the last century, one notices a sudden change in Anglican theology that took place beginning in the 1960s. In the first half of the century, the dominant Anglican theologians were people like William Temple, Michael Ramsey, Oliver Quick, Eric Mascall, Austin Farrer. Biblically, the scholars were people like E. C. Hoskyns, C. H. Dodd (an English Congregationalist), and C. F. D. Moule. The most widely read Anglican authors were probably C. S. Lewis, Dorothy Sayers, and Evelyn Underhill.

Beginning in the 1960s, we have Bishop John A. T. Robinson’s Honest to God (warmed over “Tillich”), Norman Pittinger’s process theology, Bishop Pike, and the standard Systematic Theology text is John Macquarrie’s Principles of Christian Theology. (Macquarrie’s chief influences were Heidegger and Bultmann.) Donald M. Baillie’s immensely popular Christology, God was in Christ: An Essay on Incarnation and Atonement (1948) is twentieth century Nestorianism, although Baillie seems to have thought he was defending orthodoxy. Joseph Fletcher, author of Situation Ethics, taught Christian ethics at EDS. The dominant biblical scholars in this period were people like Dennis Nineham, John Knox (not the Reformation figure, but a Presbyterian NT scholar), W. H. Lampe (advocate of “Spirit-Christology”), and, of course, J.A.T. Robinson, all of whom were adoptionists of various sorts.  The notorious volume The Myth of God Incarnate appeared in the late 1970s. The most widely read Episcopal author during the late twentieth century was likely Bishop Spong.

My colleague, Leander Harding, has been writing a book on the ordained ministry, and did some research at Sewanee on the literature that had been written by Episcopalians over the last century. In the early twentieth century, the primary content of the writing was theological. The main biblical text discussed was the Letter to the  Hebrews. The writers discussed issues like the relation between Word and Sacraments, eucharistic sacrifice, etc. After mid-twentieth century, there was a shift to the therapeutic. Episcopal writers on the priesthood now talked about ministry in terms of counseling, management, parish leadership. The previous theological and biblical content simply disappeared.

So there is a sense in which [those self-proclaimed “Episcopal Majority” clergy] who express  shock at the questioning of their orthodoxy is not surprising. If they were educated in TEC seminaries sometime during the 1960s or early 1970s, they likely would not have been exposed to historic Anglicanism, but rather to a liberal Protestantism that was new to Anglicanism, but had blossomed almost overnight, a kind of theological kudzu. I would imagine that most of the current bishops in TEC would have been indoctrinated in the new theology during their seminary days.

It is also interesting that many Anglican/Episcopal theologians who started out fairly orthodox shifted ground later on. J.A. T. Robinson was initially fairly orthodox , writing some good books on biblical theology in the 1950s. James Pike wrote a moderately orthodox systematic theology volume in the original Church Teaching Series.  Australian bishop Peter Carnley wrote some good material on the historical reliability of the gospels early in his career, but in the 1980s wrote a book on the Resurrection that was, to say the least, squishy. Richard Norris wrote some good material on Christology in the early 1980s, as well as a pretty good volume on Systematic Theology for the 1970s Church Teaching series. Toward the end of his life he endorsed same-sex blessings.

So certainly the seminaries deserve much of the credit (or rather blame) for the dominant Liberal Protestantism that is rampant in TEC these days.  Just as an aside, the vast majority of these Anglican/Episcopal Liberal Protestants who created this theology were straight white men, and they had already given away the goods before either the Prayer Book was revised or the ordination of women had been approved.