I gave you an upvote because the topics you consider are important ones, things I have been thinking about myself recently. But I have to agree with the other commenters that you might have made the posting a bit shorter and the reasoning a bit tighter. But that is enough about you and your ideas. Lets talk about me and my ideas. :)
The remainder of this comment deals with my take on a couple of issues you raise.
The first issue is whether moral-value opinions, judgments, and reasonings can be evaluated as "rational" vs "irrational". I think they can be. Compare to epistemic opinions, judgments, and reasonings. We define a collection of probability assignments to be rational if they are consistent; if they are Bayesian updates from a fairly arbitrary set of priors; updates based on evidence. We may suspect, with Jaynes, that there is some rational objective methodology for choosing priors, but since we don't yet know of any perfect such methodology, we don't insist upon it.
Similarly, in the field of values (even moral values) we can define moral rationality as a kind of consistency of moral judgments, even if we do not yet know of a valid and objective methodology for choosing "moral priors" or "fundamental moral preferences". That is, we may not yet be able to recognize moral rationality, but, like Potter Stewart regarding pornography, we certainly know moral irrationality when we see it.
Your second major theme seems to be whether we can criticize conversations as rational or irrational. My opinion is that if we want to extend "rational" from agents and their methods to conversations, then maybe we need to view a conversation as a method of some agent. That is, we need to see the conversation as part of the decision-making methodology of some collective entity. And then we need to ask whether the conversation does, in fact, lead to the consequence that the collective entity in question makes good decisions.
Although this approach forces us into a long and difficult research program regarding the properties of collectives and their decision making (Hmmm. Didn't they give Ken Arrow a Nobel prize for doing something related to this?), I think that it is the right direction to go on this question, rather than just putting together lists of practices that might improve public policy debate in this country. As much as I agree that public policy debate sorely needs improvement.
I don't think I have anything to add to your non-length-related points. Maybe that's just because you seem to be agreeing with me. You've spun my points out a little further, though, and I find myself in agreement with where you ended up, so that's a good sign that my argument is at least coherent enough to be understandable and possibly in accordance with reality. Yay. Now I have to go read the rest of the comments and find out why at least seven people thought it sucked...
Query: by what objective criteria do we determine whether a political decision is rational?
I propose that the key elements -- necessary but not sufficient -- are (where "you" refers collectively to everyone involved in the decisionmaking process):
If an argument satisfies all of these requirements, it is at least provisionally rational. If it fails any one of them, then it's not rational and needs to be corrected or discarded.
This is not a circular definition (defining "rationality" by referring to "reasonable" things, where "reasonable" depends on people being "rational"); it is more like a recursive algorithm, where large ambiguous problems are split up into smaller and smaller sub-problems until we get to a size where the ambiguity is negligible.
This is not one great moral principle; it is more like a self-modifying working process (subject to rational criticism and therefore improvable over time -- optimization by successive approximation). It is an attempt to apply the processes of science (or at least the same reasoning which arrived at those processes) to political discourse.
So... can we agree on this?
This is a hugely, vastly, mindbogglingly trimmed-down version of what I originally posted. All comments prior to 2010-08-26 20:52 (EDT) refer to that version, which I have reposted here for comparison purposes and for the morbidly curious. (It got voted down to negative 6. Twice.)