Maybe they should do background checks to see if they’re sexual predators before they start patting down little girls/boys.
There is no such thing as a comprehensive background check. In a lot of states the criminal history data held electronically is somewhat comprehensive but many times the data from county/parish courts may never get to the state repository for various reasons. Since that is the case then the data may never reach the national database level and be put in to NCIC. NCIC is the most "comprehensive" system in America. Unfortunately, like the county/parish and state systems it is lacking. It is big but does not cover everything. There is also the situation where the person has never been arrested or convicted.
The bottom line is that is if we could not do a comprehensive background check on the guy who is now president how can we do one on the possible pervs working for TSA?