Brian usually proceeds from the twin dogmas of sola Scriptura (that is, it has to be in Scripture to apply to us) and the dogma that says Scripture is a historically conditioned, human, and therefore fallen, subjective exploration of man's experience of God). It seems to me that if the latter were true, the former would be entirely irrational. If I were ever to cease being Lutheran, it wouldn't be because I ceased believing in salvation by grace through faith in Jesus Christ or the saving efficacy of the Sacraments, but because I ceased believing in sola Scriptura.
Anecdotally, this is exactly how my journey progressed. And I haven't yet bought into the notion that the Scriptures are historically conditioned, human and therefore fallen, subjective exploration of man's experience of God.
One can be convinced against sola Scriptura on other grounds and still maintain a high view of the Scriptures. The problem, as you note, is losing a high view of the Scriptures makes sola Scriptura to be nonsensical in any event. If it is what the low view says it is, why should anyone pay it very much attention at all? Maintaining the high view of Scripture, on the other hand, leaves one simply asking "who is the authority?" At least, that's where it left me. It had nothing to do with considering Scripture unauthoritative, but rather considering the proper interpretation and view of Scripture as something that ought be borne out within a tradition rather than each to his own.
And as I've pointed out before, that's exactly why you and I, or Pastor Weedon and I, or any number of other participants here and I, can have a reasonable conversation. Because the Lutheran Confessions assume a tradition within which sola Scriptura rests. We can discuss what that tradition is, who maintains it, etc.
So perhaps the real problem is the jettisoning of all tradition just because, rather than only jettisoning some tradition for cause as the Confessions do.