Nobody does that, and your demand for it is pure pedantry. If you want a philosophy of first principles you'll get to "I think therefore I am" and struggle to get much further than that. It's simply not a useful mode of analysis.and if deriving from first principles
What people actually do in debates like this is look at the assumptions underlying an argument and accept them if they are on the whole more reasonable than alternate assumptions.
You, just for fun perhaps, are trying to attack the definition of every word, and every assumption, even though you don't have any more reasonable assumption or word to offer up in its place. That's just useless, boring pedantry.
Try it, take a serious crack at this, without being a pedant:
A morality which prescribes against normal human behavior is a bad morality.
If you stop being a pedant there is so much that is interesting to discuss there--we could start in on the notion that a morality in and of itself can be good and bad, what's the justification for such meta statements? Who decides? Come on sw1tch show a little spark of imagination there, and stop being such a damned pedant. It's boring.