One could easily point out that TSA has authority over all modes of transportation, including trains and buses. In fact, TSA has VIPR teams that routinely harass, err, conduct "security operations" on trains, subways, and at bus stations. Recently outside of Atlanta, TSA was even stopping trucks and motorists, and had a portable nude-o-scope in use to peer into vehicles without owner/passenger permission (IIRC).

TSA is no longer just the agency that wants to see you naked and grope you when you fly. It's the agency that wants to see your junk all over, all the time.