Americans have died in TSA custody, children and grandmothers have been traumatized, and TSA agents abuse their authority.
The TSA engages in "airport screening" practices which have been labeled everything from invasive to unconstitutional, from dangerous to ineffective.
Cockpits are safer, and we have air marshals. Effective counters to hijacking attempts happen by the crew and passengers, not by a shakedown at the gates of boarding.