The doctrinal problem between Mormonism and Christianity is not that the LDS believe that Jesus is the only Redeemer. The problem is that Mormons don't believe that Jesus is the only God, and that there is only One God who exists.
Mormons believe that many gods exist and that Jesus is only one god amongst all of them (and not even the most important of them) which is a pagan system. How can you be Christian if you believe that there are many gods? Monotheism is a defining characteristic of Christianity.
Again, I just don’t find much in terms of intelligent discussion but moderate or hardcore anti-Mormon spokespersons.
If you go back to the early centuries of Christianity (Cnstantinople meetings), the evidence of apostasy in terms of the knowledge of God, his son and the Holy Ghost was already lost to the World. That’s where the Catholic church was derived from that we have today, and the Lutheran revisions, while good intentioned, was still coming from an apostate foundation.