King Air Captain reports a propeller contacting a taxiway light after landing when the First Officer attempts to turn off at high speed; and the Captain attempts to override him.

Narrative

After the landing the First Officer did not slow the plane down to taxi speed and tried to force a turn off the runway onto a taxiway and struck a taxiway light with the planes propeller. During the time of the First Officer making the hard turn; I was trying to correct the problem by telling him he was too fast to make the turn and I was adding opposite rudder to try to correct for the problem. I was unable to get the plane back on the runway and taking full control of the airplane; I was able to taxi to the ramp with no other problems. After shut down of the plane and looking over the propeller; I notified the Airport Manager. The First Officer and I walked over to where the planes propeller struck the [taxiway] light and cleaned up what glass we could find to get it off the runway and taxiway to keep it from damaging any other aircraft. This was a sure case of chain of events in just a small window of seconds; I still don't understand why a turn was made by the First Officer at such a high speed with plenty of runway left to slow to taxi speed. It happened so fast; I as PIC could not correct the the situation in such a short period of time.