If you are going to follow that sort of defeatist thinking that "well, since it always ends up the same way what's the point" in regards to music discussion, then could it not also be applied to other topics? And in that case, what would be the point of any of us communicating with each other at all? I see it this way; maybe every single "Discuss music here!" thread DOES end up at the same destination, but in the path that is taken to reach it, you can always find something worthwhile. Case in point, the latest thread I started. Khar, I hope you don't mind me using you as an example here -
You made it once again abundantly clear the things you don't care for, which as usual, boils down to your personal taste, but you also did so in such a way that you came across as literate, educated, and articulate. (I expect some more drunken postings to make up for this, of course) If we use you as a standard by which to judge the average "metal head", it could be argued that if nothing else, that discussion brought about a way to dispel certain stereotypes that metalheads are neanderthalic dumbasses. I think that even if that's all that is accomplished in such a discussion, it's worth the trip.
I also think that it tends to force people into thinking WHY they like what they like. Why ARE their tastes the way that they are? Speaking from personal experience, I know that these kinds of discussions have helped me articulate exactly what it is about Converge that so connects with me. They may not be your preference, and I may not be able to convince you to like them or even listen to them, but I can tell you EXACTLY why I do, beyond just resorting to "dood, they have such sic and cr00shal breakdowns, brah."
Sorry if this took a turn towards incoherency; it's late, and I should really work on sleep. Hope at least some of this made sense.