I think this forum in particular often considers self-interest as the only rational option, and so appealing to the rationality of such people as a way for ethical outcomes is a fool's errand. It's why "but it's legal" is often offered up here as a defense for companies criticised for unethical behaviour.

My best guess as to why people are so willing to act as if ethical criticisms are not valid is that the commenters self interest sees themselves as a potential future benefactor of similar actions and so they see the rational behaviour as being to defend it in case they could benefit from doing the same.

I'm not saying that people cannot ever be convinced to change their outlook here, but that doing so for an adult is a way more involved, individual process that requires input from people the person in question respects, which is way more than a university ethics course can hope to achieve.