The example of the predator and the quarry illustrates the nature and origin of self-interest and of conflict between incompatible moral values. Above all, it illustrates the indexicality of ethics

The indexicality of ethics isnt an ucontentious fact: rather, its a contentious implication of fitnessism, which is itself contentious. Indeed, some would reject fitnessism over the indexicality issue.

We are certainly not defining mugging as moral.

Although it is fitness-enhancing enough...

The idea is not to make your morals as practised as possible, but to make morals realistic, adapted and possible to practice. Ethical fitnessism is well practiced and gives guidance

.....but how does it guide, if you can refuse to accept fitness-enhancing acts as moral?

There flourishes a common misunderstanding that the function of ethics is to make people behave better, that ethics serves a purpose. On the contrary, the case is that ethics gives you the meaning of ‘better’.

Is "better" a vacuum needing to be filled? I can defined better in the most obvious way, in terms of preferences, and the purpose of ethics in terms of maximising preferences.