You're absolutely right. But so is any definition of a property. However, we need not despair over this. For one, words are just ways of referring to things in the world, and how we speak about the world doesn't affect what's really there.
Philosophers can, and have, debated over the foundation of ethics.
Some people think that these actions are the ones that are pleasing to God. Other people have their own ideas. Of course, the answer to the first question is arbitrary, but it does affect how we answer the second. And no one could argue with me on that. However, we would all agree that the set I specified is not a natural kind, because there are no properties shared by all and only the things in my set.