Great post :)

Guilt does not naturally fall out of these explanations. One can imagine a mind design that although often behaving morally for the same reasons we do, sometimes decides a selfish approach is best and pursues that approach without compunction. In fact, this design would have advantages; it would remove a potentially crippling psychological burden, prevent loss of status from admission of wrongdoing, and allow more rational calculation of when moral actions are or are not advantageous. So why guilt?

You could also hypothesize that not being authentically (like you sort of did in the second section) guilty or moral could be a burden. For an example think about how people would treat somebody who isn't genuinely guilty, and seems unsympathetic. I'm not saying that's the case, but it could be a much larger defect than an advantage to lack genuine morality or feelings of guilt. You could make the assumption that guilt related mechanisms have evolved to avoid behavior which would trigger social resentment.

The big difference between Mr. Dewey and ourselves is that where Mr. Dewey has unquestionable evidence of his commitment to self punishment in the form of a very visible angel on his shoulder, for the rest of us guilt is a private mental affair and can be faked. It would seem to be a winning strategy, then, to claim a tendency to guilt while not really having one.

I think this behavior pattern could only arise when the guilt related functions are already present in the environment. You could even further - and even more unreliably - hypothesize and describe this behavior pattern as parasitic in respect to them which could in turn result to a ratio of frequencies... Or maybe that's a longshot.

Although this could theoretically be mediated by the behavioral strategies of a sufficiently intelligent and Machiavellian unconscious mind, it fits within the framework of evolutionary psychology and can also be interpreted in evolutionary terms.

I think this section could be met with similar responses as the previous quoted sections. But I would like to add also that there are people who are not genuinely sympathetic, who may or may not be empathetic.. :(