While alcohol does in fact reduce doubt and insecurity, I wouldn't jump to: any crude global brain impairment is likely to first impair self-doubt/monitoring.

Otherwise, nice pep talk.

If a fuzzy definition becomes a massive problem, then that definition clearly wasn't in existence merely to simplify speech.

Regarding mammals, is there a use for the term that requires its inclusion of dolphins? Does the existence of sweat glands usefully separate mammals from other animals? After all, mammals in general share a variety of properties: most give live birth, most have hair, most are warm-blooded, etc.--but we admit to the category of mammals many animals that fail one or more of these criteria.

A well-defined but useless category (I am not arguing that "mammal" is such a category, as there may well be a biological use for it) may be pedagogically interesting but otherwise may merely confuse our understanding of thingspace.

Which weighs more: a pound of feathers, or a pound of gold?

[...rationality discussion...]

I must be missing something. I thought the point of this riddle was the difference between avoirdupois and Troy weight -- a simple matter of (rather esoteric) factual knowledge not contained in the structure of the question.

Questions about a property rarely contain their own answers in a trivial way

I think this fact may explain most of the reaction; the answer is slipped into the question with a couple words that don't interrupt the flow. The questions is pointless, but we don't expect questions to be pointless, so we don't really hear it right or interpret it correctly, and we answer the question that would actually make sense.

At what point do we say that the problem lies in the definition of a category? Since ordinary people have no especial use for the category "bird," it's unsurprising that they haven't nailed down characteristics that would allow such a use.

Categories that we need--that must reliably possess some characteristic(s) such that they are useful--tend to have strict necessary and sufficient conditions for inclusion. Categories that we use purely to simplify speech can get away with fuzzier definitions.

Is the dolphin really a fish? That depends: is that thing over there really a blegg?

This looks sincere to me, and given that it's sincere, people really ought to be allowed more chance than this to recover from their mistakes.

I say that depends entirely on the nature of the mistake. Gross negligence should not be forgiven, although the proper response is not necessarily retributive.

This could be criticized as trying to find an argument that fits the conclusion, but I think this is uncharitable.

I think it's exactly right. All reasons are rationalizations.