Nor should you agree with that. It is an example of a faulty syllogism, just as the example I made was. What Imaro demonstrated, AFAICT and IMHO, is that D'karr's reasoning relied upon a similar faulty syllogism.
And, as you did above, pointing out that a line of reasoning relies upon a faulty syllogism is not "cheap verbal prestidigitation". It is, instead, one of the most important means by which discussion can be rendered rational.
Perhaps I wasn't clear in demarking the example you quote as being a false syllogism?
No, you were quite clear. I wasn't, however, talking about pointing out that someone's reasoning is faulty. I was referring to the fact that doing so by taking it to an absurd extreme often leads to a less, not more, rational conversation.
Let me clarify my point.
-We are discussing the difficulty of grid vs gridless, and the complexity of combat in 4e as compared with earlier editions.
-Since several people have claimed they possess the capacity for running without a grid in both 4e and earlier editions, we can reasonably assume that at least some people are capable of running D&D without a grid regardless of edition.
-It's also been claimed that running D&D without a grid is a skill that can be learned. This matches my experience as well, and I think it's reasonable to say that there is at least some truth to it.
-Therefore, comparing running 4e gridless to trying to swim in a raging river that would sweep an elephant away actually misdirects the conversation, because it suggests that doing so is either impossible, or at the very least superhuman, which doesn't seem like a very reasonable conclusion based on the above.
The marathon analogy (running 5 vs 10 miles) is better, though it still suffers from faults that most analogies suffer. That being, it's only the rough sketch of the point you're making, and nothing more. In other words, if I can only run 5 miles competently, then running 10 miles is either impossible for me or at least a serious physical strain. Remembering the relative positions of 5 vs 10 minis doesn't compare on any serious level.
Both 4e and 1e have their respective complexities. While it isn't unreasonable to assume that different people might have an easier time with one than the other, it
is unreasonable (IMO) to assume that one could not learn to run either.