I don't think this thread serves any purpose (perhaps 20 years ago) as in a Multi Crew environment in the 21st century most if not all the younger FO would I like to think be assertive enough to challenge any potential issue.
Maybe if you actually read the thread....?
Dave, who's Profile states that he's a qualified airline pilot, posed the question : "What if he/she carried on with the dangerous thing?"
As I understand it, his question is not just about taking control, but taking Command. Challenge doesn't necessarily resolve a conflict, despite the impression often given by conventional CRM teaching.