I don't see where you get the "everyone". The TSA doesn't frisk "everyone" - just people who are about to get on board the 400 ton missiles we call commercial airplanes, next to which a 1 ton JDAM is a pinprick.
Public safety departments - even one as large as the NYPD - don't have unlimited resources. If they abuse their power, we can force them out of office and even put them in prison. That's why we have elections - so we can put our collective foot down. 20% is a huge success rate. It represents over 100,000 arrests of actual criminals.
You need to get up to speed. The TSA is operating at many public places now not just airports. The ‘safety’ philosophy IS spreading. Also the police don’t arrest ‘criminals’, they arrest suspects. Again, according to your logic, if the authorities were to ‘stop and frisk’ twice, three, four times as many people would they not be taking more potential ‘criminals’ out of circulation? The theoretical logical conclusion being if everyone was suspected and frisked, crime could become almost nonexistent. Maybe NYC needs to add some additional taxes and hire more law enforcement in order to really bring the crime rate way down. That little thing about unreasonable search and seizure is just so passe.....