PIC is denied entry back to his FD
"His" flight deck?
Did we not leave this kind of "I'm the Captain so I own this aircraft and you are just here because the regulations say we need a body with a pulse in the right seat"-attitude back in the 1980s...?
With the information available so far, and I repeat - SO FAR, it seems to me that the FO did exactly what he is paid to do, act in the interest of safety of the aircraft, passengers and crew.
CP