You need to do certain things in order to hold a rational discussion, just as you need to do certain things to play chess. I don't have to concede that you can win a chess game without putting my king in check, and I don't have to concede that you can support a conclusion without arguing the points that need arguing. Of course, you don't have to play chess or be rational in any absolute sense. It's just that you can't have your cake and eat it.

Categorical good and evil is a different concept to the hypothetical/instrumental version: the categorical trumps the instrumental. That appears to stymie one particular attempt at reduction. There are many other arguments.