When I was born, 30% of all Americans attended mainline denominational churches. Today it is less than half that. The mainline denominations capitulated on orthodoxy long ago rejecting biblical innerancy, miracles, etc. and then began to concentrate on social revolution. First it was female ordination, which emptied the church of men, and then, overturning of the sexual order. So, where has this led?
The Presbyterian Church, USA has grown more liberal every year since their founding in 1983 and this produced the fruit of a decline of 50%. Look at this chart and notice that they have declined in membership every single year since their founding. Every single year! This is atrocious and testifies to earlier problems that were sown. Masculine leadership would never have allowed this sort of malfeasance in any organization. The only place where this happens is in overly-bureaucratized institutions where no one takes responsibility for anything.
So, having homosexual bishops who have divorced their same-sex "spouses" (like The Episcopal Church) or putting up a ballot at your General Assembly to affirm same-sex marriage is simply a sign of the hollowing out of Christian belief that occurred earlier. In the end, why would anyone want attend a Christian Church that is about as un-radical and culturally conformist as your local college LGBT support group or school PTA. The answer is they wouldn't.