So I suppose it's possible that a professor with controversial opinions ended up on a no-fly list for some reason completely unrelated to his politics. Occam's razor, though...

There are other abuses that we have concrete evidence of. E.g., refusing the cooperate with the FBI. (https://ccrjustice.org/home/press-center/press-releases/laws...).

Hell, up until 2005, the TSA used CREDIT SCORES as a component in deciding who should be on no-fly lists...