If anyone actually believed that their 4th amendment rights were being violated, then why would they not sue? Or better yet, seek the help of the ACLU? Where are the lawsuits?
The Supreme Court has already covered this with their ruling on "implied consent." You already KNOW your bags are subject to search, that was true pre 9/11 in case anyone forgot. The airlines had complete control over what went on "their" aircraft before 9/11 and did searches.
Why anyone would think that a screener who finds a human head (to bring back a tired example) should just turn away and "forget" that he found it is beyond me. Two glazed eyes staring at me would not be something I could easily forget, much less the shocked expression on the face that would obviously be there.
If you do not agree with the policy and actually believe that your rights are being violated, you have options. You can sue (good luck), you can quit checking bags, or you can drive to your destination, (conditions permitting of course). I have yet to see anyone forced at gunpoint to check a bag, or fly to a destination.
I do not see the policy going anywhere in the near, or distant future.
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"All life is a concatenation of ephemeralities" - Alfred Kahn, American economist