"Ethical" does not mean "good", "moral", or "right", it means something more like, "consistent with an explicit set of ethical axioms." It's meaningless to say something is unethical without stating or at least implying a specific ethical philosophy.

Carnism says that it is sometimes acceptable or even good to be cruel and violent to animals. Veganism says that it only is in cases of absolute necessity. A researcher or scientist for a cosmetics company might follow all the ethical requirements of their profession, and yet by any other standard, do unforgivable harm both to animals they experiment on and to the humans they mean to exploit with their research.