Objection was not an option? What would they do to someone who objected, throw them in the company prison? I suppose they could threaten to fire someone, but here in the US, I feel like that in itself would pose potential legal issues for the company.
I'll be damned if I ever let anyone, an employer or otherwise, "clean" a personal device of mine because I inadvertently received classified information, through no fault of my own. The only exception would be if they had a search warrant, which, somehow, legally authorized them to do so.