> "Let me ask you this: say you want to check for guns and explosives before people get on an airplane. How do you do it?"

Politely. With the view that I'm dealing with people who are innocent unless found to be otherwise.

Edit: Please also note that permethrin is not an explosive. Should everyone who uses insect repellant be treated this way while going through security? I'm surprised the guy even knew the name of the chemical (I wouldn't have).