Perplexed wrote earlier:

Morality teaches you when to punish and reward (and when to expect punishment and reward). It is a second-order concept, and hence not directly tied to preferences.

Sometimes you'll want to explain why your punishment of others is justified. If you don't want to engage Perplexed's "moral realism", then either you don't think there's anything universal enough (for humans, or in general) in it to be of explanatory use in the judgments people actually make, or you don't think it's a productive system for manufacturing (disingenuous yet generally persuasive) explanations that will sometimes excuse you.