I would think, I thought that my denomination surprised me when Spong was allowed to retain not only his Bishopric but his cathedra seat with his "theology", that the Creeds and the Westminster Confession would've stop a preacher such as that from getting accepted in the PCUSA? Liberalism is one thing, but moving completely from Scripture is another thing entirely.
The problem is that liberal Christianity does include Spong.
As I understand it, liberal Christianity started as a response to Kant, the Enightenment, and new critical scholarship. This was all in place by 1800 or so.
I believe there are two 19th Cent streams contributing to liberal Christianity, one that is often credited to Schliermacher and the other which doesn't have any one source but is often credited to Ritschl. My highly oversimplified version is the Schliermacher thought that the traditional Biblical picture had become untenable, and replaced with it a generic God-consciousness, of which Jesus was a primary exponent. Ritschl was part of a tendency to accept the results of critical scholarship and build Christianity on Scripture as understood that way.
In my view, a third strand is there as well, which I'm going to attribute to Barth, though he certainly didn't invent it. But it's the continuing presence of the Reformation heritage, although in a new form.
I don't think we can read Spong out of liberal Christianity without doing too much violence to our tradition, and rejecting a number of distinguished theologians. As far as I can tell this is an updated version of Schliermacher and Tillich. I am *not* an admirer of Spong. I find him a shallow representative of people like Tillich, and that's not the part of the tradition I'm part of anyway. But still, he is within the traditional scope of liberal Christianity. Nor does he reject Scripture, though I find him a bit too cavalier about dismissing its assertions. I don't think theism is untenable. He does.
His is not my personal approach. Furthermore, I don't think historical Jesus scholarship as it developed since 1800 justifies the kind of skepticism that would lead one to see all signs of a theistic God as vestiges of early misunderstanding.
But the fact is, it's there in the tradition. Would the PCUSA reject Schliermacher or Tillich? I don't think so, and I don't think we should, even though I disagree with them. (Incidentally, I didn't always -- I accepted Tillich's approach to God for much of my time in high school, while remaining an active Methodist. I'm not prepared to say that I wasn't a Christian at 16.)
I'd still like to see more of what Sandlin has to say before judging him, but even if he is equivalent to Spong, I'm not sure the PCUSA would reject him. I do think he has to say something about Jesus to distinguish himself from a generic theist or deist. But you might well not accept what he has to say.