He lied because if he had said "peaceful," then the roles of Doctor and Player would have been revealed (everything can't be true).
Or could he? Okay, GM, please clarify: are all the answers in binary form, yes/no?
Added 6 minutes later
And the guard could have taken points, and then he would have approached, but a notebook would probably have been a better choice for him.
e si ieu muoir, er mi grans deliuriers