This was an aspect of Tolkien's work I always admired greatly. One of the best examples of this sort of thing is probably The Council of Elrond. Many find the section boring and long winded, but I think it's cleverly crafted and painstakingly thought out. We get many differing opinions, each is given the chance to run their argument through. A rare occurrence these days
This is probably down to Tolkien's environment as an academic. Being familiar with each side of an argument is essential to constructing your own, and in reading Tolkien's essays one gets the sense he understood this very well. When this goes over into his creative work I think it compliments his world greatly and is one of the many things that makes Middle Earth come alive.
In cases such as the Erebor argument, Turin's 'bad luck' and even the voice of Saruman, I think we get the very subtle 'grey areas' of Middle Earth. Many people like their morally grey things to be played out in specific characters, but I think Tolkien's genius is right here in the unclear areas. Here Tolkien is pointing out that it's not always so clear cut as you may think; there are different opinions to consider, different angles to take and different attitudes sported.
It makes the world of Middle Earth that much more real. In real life there are the uncertainties and each opinion has its champions.