They can still ride, just not operate, which is what requires the license.

No license is required to be a passenger in a car or on an airplane.

Yet, on planes your travel even as a passenger can be restricted with no due process, judicial oversight and sometimes as a double punishment.

I mean, if DHS or other TLAs flag a person as a threat, they should be able to do something about it... just not "you are on a list now because we say so" and no oversight or appeals process. This is not liberty or a free society. In a free society you don't have "national emergency" that spans multiple generations (20+yrs now) that allows overriding peoples rights and liberties.

The airlines should be allowed to refuse service so long as they are not coordinating a ban list, and even then.

Better analogy would be for public transport passengers.