The point here is largely that reality (at our level) is not something which can be simply solved by the application of a couple of rules, from which Right Action will thenceforth necessarily flow.
Reality is a big, complex, ball of Stuff, and any attempts to impress morality upon it will be met with many corner cases which produce unwanted results unless we spend our time engaged with dealing with what initially look like tiny details.
I'm sure you can find a compromise in the middle of "Mostly follow some vague rules, but when they lead you to what seem to be negative outcomes think about whether it's because you don't enjoy doing the moral thing, or if it's because actually it's led somewhere unpleasant and you need a new rule for this situation."
It's even worse. People are exceptionally good at rationalising whatever it is they want to do and turn them into convenient rules that sound noble and high-minded.
It would be a much less frustrating world if the robber who takes your money would just tell you "hi, I'm taking your money because I can and because I like it" instead of earnestly believing that he deserves it for some complicated reason (pick your example).
Reality is a big, complex, ball of Stuff, and any attempts to impress morality upon it will be met with many corner cases which produce unwanted results unless we spend our time engaged with dealing with what initially look like tiny details.