He flashes his teeth. The fact that she feels the need to point it out is a little funny by itself. "Don't worry, I can tell."

"They train the humor right out of you in the army?"

Maybe it's insensitive. But Firo's never been particularly concerned with stepping on people's feelings, and he doesn't know much else about her to joke with. If he knew she was from Milwaukee, he'd just ask if people in Milwaukee didn't have jokes. But all he really knows if her profession and the fact that she randomly gives meat to people. So kidding about the job it is.