I'm actually a stickler for ethics in general, and honestly, I don't see any violations at all other than the leak/publication part.
Players aren't infants. They understand now that the sport they love to play is a business at almost every level. Most of them were already practically playing "pro ball" before they even got to college. I think some of this sentimentality is just nostalgia for an era of amateurism, and I share a lot of that, but that's not reality. What's happening now is reality. And every actor in this play is aware of it.
I've suspected for some time that Moos saw something in the program's culture that he didn't like--I have no hard proof of that, so it's worth what any other ill-informed opinion is worth--and acted on it when he could. Much of this purge supports that perspective (but it also supports other perspectives as well, just to be clear and fair). But if you're going to hire a new coach to change the trajectory of a program, they have to have the freedom to do that. And Hoiberg's doing what he's literally being paid to do. And there's nothing unethical about that. Ethics isn't a euphemism for "easy landing" or "getting one's way". To me what would be unethical is if he retained these players just to honor their previous commitments and then let them languish on the bench for the remainder of their careers without telling them that this was their fate when he arrived. *That* would be unethical. And that's not going to happen.
Even if you don't trust Hoiberg, trust Doc. The dude's moral compass is on pretty tight. He's not going to sit by while a player is abused or mistreated in any way shape or form.