A note from my side of the universe in software: it is far more productive for a software team to fire a member who is disruptive no matter how brilliant or productive they are, allowing "that guy" to stay poisons the workplace and undermines your authority.
The hardest part of being a manager, as told to me by various managers of mine over the years, is disciplining or firing someone and yet it must be done. Having clear guidelines from HR helps keep the process professional, as I learned from my ex who was in Hospital HR for years.
Nurses eating their young is not "culture," it's just wrong. Who knows, with a formal paper trail your recalcitrant nurse may turn it around and teach instead of threaten.