Some people believe that lies to immigration officials are acceptable, others feel that one should answer honestly or not at all. To the extent that "naive stupid" means the same thing as "honest and principled", you are correct. Perhaps he should have sought legal advice before entering, but I would presume that the author made this choice consciously based on his personal values. I wouldn't insult him by calling him naive and stupid unless you are certain your personal values are better than his.