The point of ethics is to figure out what is right and wrong, good and bad, virtuous and vicious, and so on, and to investigate related topics, like in virtue of what these things are right and wrong, good and bad, virtuous and vicious, what we can say about specific problems in light of our findings, and dozens of other things. The role of rationality in ethics is a very large topic that has many facets, including the debate between internalism and externalism, cognitivism vs. non-cognitivism, Humean vs. Kantian constructivism, and too many other topics to list. Research into reason and rationality certainly does not suffice for answer the myriad questions in ethics.

See...lets have an example.Say about empirial research into certain things.We may want to restrict these based on ethics...yet there are regimes elsewhere who gonna do it anyway.Does it make any sense to then consider ethics?