But I didn't see the gen'l talking about common sense (a wonderful sense, though we humans just don't catch it all). I saw him talking about the utopian concept of ultimate objectivity.
But then he seems to make the mistake of assuming that because we can't prove truth to complete conceptual satisfaction within the human box, the matter of whether or not someone is outside the box doesn't matter to him.
I'd ask him, why is it that truth is so important to us, yet we realize we are too limited to be certain of it by what we can discover depending strictly upon our conceptual souls?
Well, it doesn't matter to me, because the question of whether someone is outside the box is ultimately a question of where we should start understanding what morality is or should be. I'm a results-oriented kind of person, and so it seems to me that the ultimate goal of morality is to make us better people and to make the world a better place - the question of whether moral propositions are true or not is ultimately less interesting than the question of whether they are useful or not, in no small part because the question of truth does not appear to be amenable to investigation. I could be wrong, but I think I'm pretty well insulated against being proven wrong any time soon ;)
Now, at this point, having laid out my cards, I've probably managed to create a platform that very few people are actually interested in occupying - objectivists will pretty clearly object to my dismissal of objectivism, and if you look at it, you'll probably see that this position is rather dismissive of theistic brands of morality for pretty much the same reasons. Everybody tends to ask themselves "is X true?", and the answer to that question will determine your starting point for what morality is based on and what it ultimately is. But the question of "is X true?" does not seem to me to be fruitful, and so I ask myself "is X useful?"
So really, the question you're asking me is "why is ultimate truth so important to other people?" And for that, I have several answers. One is that the ultimate truth about morality really exists and really is discoverable, and sooner or later someone will hit on it, and that humans have an instinctive sense that this goal is attainable. I tend to doubt that one myself, but I can't really honestly dismiss it either, so I at least consider it a possibility, albeit a rather remote one. The second answer is that people concern themselves with ultimate truth not because it is necessarily discoverable, but because the act of investigating it is itself inherently worthwhile in some objective sense - the act of investigating ultimate truth serves to improve us in some objective fashion, even if we never actually attain it. And further, that we know this to be true and act upon this true belief. I suspect that this will prove to be a rather popular option, particularly since I've seen it expressed nearly verbatim in places.
The third answer is somewhat more cynical, in that humans are concerned with the question of ultimate truth because of what it brings about within them in a somewhat more selfish sense than the second answer. People investigate ultimate truth, whether it is or is not really knowable, because they like the subjective feeling of security and knowledge that it engenders in them - whether consciously or unconsciously, they do it because they like the warm and fuzzy feeling that insider information usually brings. And the fourth possibility that I see is the most cynical of all - people are interested in ultimate truth simply as a means to a preferred end. Consciously or unconsciously, ultimate truth is treated as a stick to beat people with. That's a rather ugly thought, but people can be rather ugly sometimes, notions of morality notwithstanding ;)