So, I asked him - how can the agency justify some of their more egregious practices? He laughed and said "you don't get it - their view is that we will push the outer boundaries of our authority until someone tells us to stop." They view their authority as broadly as possible, and figure that if they've overstepped any, the courts will rein them in. In other words, no one in DHS is acting in a supervisory capacity to ensure TSA personnel aren't violating a passenger's Consitutional rights. It's up to the public to challenge them at the checkpoint, and decide to take their case to court.