I don't agree with Don Cupitt's views of Christology (he underestimates a high christology being present early on, especially in the writings of Paul), but I do think he has an interesting perspective on what makes Jesus' ethics different from Judaism or Islam. I also agree on many points about the imperial synthesis of Christianity based on hierarchical, authoritarian power structures. I think that's one of the things that Luther was reacting to, ultimately, and it's something that has only been more realized in the post-WWII era by certain theologians.
First of all, a disclaimer. Listening to something is, for me, the worst way to learn and understand something. Reading is far better for me. However I did listen to the discussion linked in the post. I also did a small bit of research on the Cupitt.
I don't find his discussion of Jesus as a philosopher to be out of line at all. While my path from Christianity to a secular view of Jesus is not as extensive as Cupitt's, a lot of what he talks about became clear to me over the years.
One of the things I did once was to read the gospels in the order they were likely written instead of the order they are in the bible. The order I used was Mark, Luke, Matthew and John. One could argue Matthew before Luke but, as I understand it, they are considered to be written about the same time.
I also did the reading 'for pleasure'. By that I didn't attempt to analyze any of the passages. I read them like I would a novel. I also used The Message in my reading since it is better designed to be read as a novel.
As I reflected on the experiment, I realized the Bible is 'hiding' the beginning stages of the legend building which resulted in the Fourth Century's Deification of Jesus as God Himself. That final stage in the Fourth Century effectively locked Jesus away in Heaven and made room for human 'interpreters' to control the religion.
But the beginning of the process is recorded in the Gospels as, over time, Jesus appears to gain more and more aspects of a divine being. There is a reason why people who use the Bible to defend Jesus as God only seem to use the Gospel of John. It was the last to be written and was written at the very end of the First Century. That is some seventy years after Jesus lived on earth and represents seventy years of legend building as some three generations of Christians told and retold the stories of Jesus.
Mark, OTOH, doesn't include the divine, worshipful respect of John because it was written much earlier in the legend building process. In Mark, Jesus is far more human than divine.