Just because nutjobs like to try to invoke constitutional rights doesn't mean those rights don't exist and can't be helpfully invoked. The stereotypical nutjob-invoking-constitutional-rights move is to respond to every police encounter by asking, "am I being detained?", but sometimes you're better off asking that question.

He kind of has a point, though -- I agree the right to travel does not specify a specific mode of travel and should cover planes, but then pretty much everything that goes on w.r.t. planes and cars is unconstitutional.

(Consider that while the government definitely has the right to tax you for road use, requiring you provide an ID to prove you paid a tax is like requiring you to carry an ID proving you paid your federal income tax, or requiring an ID to exercise free speech.)

"Am I being detained" is level 1 nutjob stuff, fairly normal. Incorrectly invoking a "right to travel" is advanced nutjob. It will immediately make a lawyer think you're a sovereign citizen since that's a cornerstone of their legal philosophy.

Its from the "Privileges and Immunities Clause" of the US Constitution and has shown up in many court cases. What may seem "nutjob" to you might have a whole different meaning to the lawyer you have hired to protect your company. Which is why you really want to make sure the letters that you get from lawyers are ran by a lawyer even if they seem a bit off.

Probably, but they would not do the same for your lawyer and a few well placed media mentions.