Yet Another Day in the Life - S6-E22
Continuity mistake: When Mac calls the Becker case, Harry is holding a pencil. The shot changes and he is no longer holding the pencil.
Yet Another Day in the Life - S6-E22
Continuity mistake: During the case with the Star Trek fans, in one shot the gavel in front of Harry disappears.
Answer: It's possible when Harry called the military, he implied that the book contained sensitive information, seeing as how many government and military officials were part of the client list.
I thought it was because he developed feelings for the madam and couldn't bring himself to turn her in.