First of all, if they really had the authority to do this, they never would have worried about it. Here’s a thought experiment. Suppose a police officer (you know, a real law enforcement officer) decides to, with legal authority, give you a pat down. A real patdown involves more than just brushing the genitals. It involves a full on groping, by necessity.
Tell that cop, “if you touch my junk, I’ll have you arrested for sexual assault.” What is that cop going to do? He’s going to say, “tell it to the judge” and then he’s going to do his pat down anyways. Why? Because he actually has authority. The TSA balked. You know why? They know they don’t have the authority to do this.