When we talk about an ethical core, that sort of behavior exists between individuals. People in a family, or people who are friends, hopefully will and typically do adjust their behavior according to some sense of ethics. When we put people into a classroom, however, we’re implicitly putting them into competition with their peers for a limited set of opportunities that determine the extent to which their basic human needs, and those of their family, will be met in the future. Let me ask you, what is it about one’s ability to perform well in some arbitrary social role that makes them more entitled to their needs being met than another who lacks that particular ability? If you wanted to argue that a cheater is behaving unethically, you’d need to show that they do, in a moral and ethical sense, deserve less than their peers.
"Deserve" is a subjective and poorly defined concept. They agree to the evaluation criteria when they take the course. They are supposed to actually learn the material. Everything else in your argument is sophistry.
You argued the similarly subjective and poorly defined notion that students who cheat must lack an ethical core, which is why I decided to discuss fuzzy things like ethics rather than the obvious fact that they signed an academic dishonesty agreement. Why is violation of said agreement something that I should view with disdain/why does it say anything about the ethical core of the student?