I have yet to read a convincing explanation as to why I should give up my rights simply because of my mode of transportation within my own country. There is nothing stopping a terrorist from showing up at an airport armed for bear, and there is no benefit to making sure I don't carry any shampoo or nail clippers through a checkpoint.
Let me lay out a scenario;
I am a private pilot, and have been since before 9/11. I own a plane with a range of 1,000 miles, give or take. I'm not supposed to, and it's technically illegal, but to help pay the bills I sometimes give folks a ride to the large regional airports nearby. It is a fun flight for me, and they don't have to park their cars far from home and pay the high fees. A stranger chats me up about taking such a trip, he and his friends are going fly fishing. A few weeks later, I meet them at the airport, help them load up their luggage into the plane, take a few hundred bucks in cash, and take off. I do not know what is in their bags and boxes. we have passed through no security screening whatsoever. In fact, we have interacted with no one else all day. I am carrying three crates of RPGs, automatic rifles, and explosives to a major international airport.
My airport is not controlled, so I have no tower to report to as I will at our destination. We fly for an hour and a fifteen minutes, covering one hundred and sixty miles. My passengers chat with me over the intercom about things on the ground and about their trip. I am not suspicious. I approach the major airport and make contact with the control tower. My passengers are getting nervous, but I put it down to small-plane jitters. I get clearance and land at the small private aviation runway, some distance from where the commercial flights land and take off. Guess which side of the metal detectors, bomb sniffing dog checkpoints, nude scanners, and x-ray machines we are all on?
My passenger reaches over, unplugs my headset, and puts a pistol to my temple. "Taxi over there." he says, pointing toward the large airliners. I refuse, but they have seen me taxi to our current location, and know more or less how to maneuver the small plane on the ground. The terrorists shoot me and taxi the plane to the commercial section of the airport. You see it on the news the next morning.
This is but one of many holes that are not addressed in the current airline security model. The result is largely symbolic and pointless harassment of law abiding people and the apprehention of a few incredibly stupid terrorists, often by passengers after the plane has taken off.
The TSA is woefully inefficient and should be abolished in its entirety. It does little to protect us and breeds a culture of docility and obedience unfitting of Americans.