I basically consider this technique to be "advanced politeness--" while it obscures my true meaning at first, it seems to ultimately help that meaning take hold in conversations with people who are inclined to become combative or argumentative at perceived insults (which is really most people).

I absolutely agree with this - being one of those people who "are inclined to become combative or argumentative at perceived insults" myself (by chance, I suppose, I have spent most of my time when debating, debating in the bar-fighter way, rather than as part of a true dialectic). Part of what governs my conduct is having nurtured my image as "that guy who will damn-well tell you what he thinks of you, whether or not it makes you cry" IRL, for several years. I think it probably really is the case that, by being polite and kind, you're more likely to change other peoples' minds. However, I'm wary that a certain kind of honesty may be undervalued here - if I thought that someone thought I'm an idiot, and they weren't telling me, but instead being nice in order to change my mind, I would be livid. I would hunt you down, and I would make you weep, and then I would make your parents weep for what became of their child. I would not be happy at all. Advancing that same respect to the idiots I disagree with is really important to me - whether or not it is the most effective method of changing their minds.