“Radical fringe”? Ridiculous. These are well-respected, well-established scholars. (What that tells me is that Mr. Boyd can’t refute them, so he needs to try to marginalize them.)
These are scholars with many books, classes, much research, and many of whom have examined actual manuscripts. They’re in an excellent position to know what they’re talking about. They use the rules of evidence in support of what they say. Your scholars don’t seem to be doing that.
There is little evidence to support what you call “the authority of the gospels.” It’s based on nothing but faith.