etiquette and ethics
Ethics are the answers to the question of what ought I (or we) to do? But sometimes the answer doesn't seem to have anything to do with ethics. "What ought I to wear?" is a sartorial question that has to do with style and comfort, and only minimally to do with ethics. "What ought I to eat?" has to do with taste and nutrition, and only minimally to do with ethics. Etiquette seems to be a third category of answers to "what ought I to do?" that is only minimally about ethics: ought I to hand write a thank-you note instead of texting?
There are examples of clothing and food and etiquette choices that are ethical: wearing leather, eating meat, and requesting a meal without meat might have been stylistic, gustatory, and etiquette questions at some point, and they still are to some extent, but those are also ethical decisions now.
In my intro ethics class, I don't focus on grand ethical problems for two reasons. The first is that large ethical issues are usually policy issues: what ought we to do about abortion or gun control, about regulating companies or banning private behavior with social costs? Policy questions make us think abstractly and impersonally, which is perfect if you're making decisions abstractly and impersonally the way that we might want our government to do it, but it's not the way that we would want our friends to decide what to do, and treating a friend in an abstract and impersonal way is probably wrong, in addition to being a bad way instrumentally to keep a friend.
The second reason is that it makes it seem like ethics questions are the big questions, and answers to all the small and medium questions are therefore discretionary. As long as you're not killing anyone or even discriminating against people, then ethics has nothing to say to you about your choice. Only when you risk hurting someone do you need to think about ethics, and ethics is more like a checklist of regulations to go through before finalizing a decision.
That orientation towards ethics is wrong, and, more importantly, it removes any understanding of why we ought to care about ethics, since ethics is just another thing to think about when making a decision: etiquette, taste, style, and ethics. But ethics is our orientation to making any decision, not a set of things to consider in making a decision.
This does leave open, though, that some decisions are entirely gustatory or sartorial or even purely questions of etiquette: whether to put mustard on one's own ice cream, wear stripes and plaid together, or hand write a thank-you note.
The way these questions are the same as the questions of whether to wear leather or eat or serve meat is that we can ask the question of "what ought I to do?" for any of them. The way they differ is that "what ought I to do?" is here elliptical for the longer question that ends with "...in order to live a good life?" and that question might be harder to answer in some cases than others.
When I ask whether to wear leather or eat animals, I'm considering how compatible having a good life is with looking a certain way and tasting certain things. But I could be fully committed to having a good life and not have any idea about whether to put mustard on my ice cream. The flavor combination would be novel, but probably bad. I'd have an entertaining story for friends, but they would wonder about me. So I could answer the question of what I ought to do in order to have a good life and not know whether to put mustard on my ice cream. There might be a right answer that would be most compatible with a good life, but I don't know the answer not because the case is too complicated, but because there just doesn't seem to be much more to think about: it's novel but bad, entertaining but weird. That's the end of it, and I still have to decide what to do, but there's nothing about having a good life that I know about that's going to settle it for me.
So the concern isn't about which cases are "purely" taste, but about how we answer the question of "what ought I to do in order to have a good life?" Style and etiquette might be how we express respect, for example, and expressing respect can very obviously be part of a good life, so some style and etiquette questions have answers that tie directly into questions of respect or fairness or community, all of which are clearly ethical questions. And sometimes respect would pull us one way and fairness pulls us another, in which case we have an ethical dilemma of some kind. But the underlying question in all of these cases, easy and hard, remains the same, even if what we draw on to answer them changes, and the difference between ethics and etiquette might be nonexistent.