[sixo]

It's difficult to have a productive, thoughtful conversation when someone reads a moral imperative into the phrase "supposed to" and starts lecturing about it.

The sense of "supposed to" above is: the human system was "designed" for a certain environment, and its behaviors make sense there. Outside of that environment many behaviors won't make sense, but can easily be explained by reference to the original environment. This is not a moral point, although it is one often employed in moral arguments.

[xyzzy_plugh]

Your explanation makes sense but wasn't remotely my interpretation. I'm still unsure if I can interpret it as such.