Father Bill: Assuming I understand your post correctly, what you suggest about establishing a distinction in the rules between substantiated fact and advocacy/opposition makes a lot of sense in principle, but would be very difficult, if not impossible, to implement successfully in practice.

Take the relatively dry, precise subject of science, for example. Start a discussion about "global warming" and ask participants to confine their comments to facts, not opinion. There will be a short distance between the statement of the first "fact" and the first lively argument about that "fact". Now, switch the subject to one of politics or religion and the problem grows exponentially.

Even if one confines the discussion to a comparatively simple topic, like kilts and Scottish attire, and insists on the use of simple, undisputed facts, like "blue and purple are two distinct colors", ... oh, never mind. ;)

I think it's best just to avoid some topics as the rules stipulate.