—...without the shelter of “devotional” and “caucus” threads, polite discussion of theology is not possible...—
Actually, a more accurate way to put it is “without the shelter of “devotional” and “caucus” threads, disagreement is not possible”
That is because you can’t even disagree. So what is the purpose of the thread in the first place but to pimp a blog or site? Why not just lock the thread as soon as it’s created?
The purpose of a "devotional" or "caucus" thread is for folks who generally agree with each other to discuss their theology without constant interference from those who disagree.
The purpose of an "open" thread is for folks who disagree with each other to compare and contrast their beliefs, air their disagreements, defend their beliefs, and attempt to disprove contrary beliefs.
Both are necessary. The labels are necessary because some FReepers seem to suffer from an obsessive compulsion to vent their spleens upon those with whom they disagree.