In short, keeping a U.S. citizen off of airliners because of their political persuasion or because they might join a LEGAL demonstration is a VERY BAD IDEA, particularly when it can be done secretly, for reasons unexplained, and without recourse.
By the way, I am a strict constitutionlist, and somewhere to the right of Attila the Hun when it comes to enforcing our laws.
And your point is?.
---max