The two-pin plug should have a green ground wire attached to it. This green wire must be attached (grounded) to maybe the screw attaching the faceplate to the outlet box. If this is not done, a potential hazard will be created.
He is trying to unground one of the devices since its getting a second ground thru the other device. Ive done this in the past with no issues as the electricity still gets ground at the fusebox. I'm guessing he is trying to unground the monitor since I dont recall a laptop charger coming with a 3 prong plug.
If the monitor has any exposed metal surfaces be sure you ground it again with any other use.