You are assuming that the sky marshals are telling the truth. To whom did he give the thumbs up to? That person should have been arrested too. Or did he just give the thumbs up to the flight attendant? Did he nod his head or speak to anyone on his way back to his seat? Or is that against the law too.
You're a friggin idiot arent you?
I know that in the schizophrenic world of Contrarian Treky conventions you are taught to pull magic reasons out of your wazoo as to why we all should second guess authority or obliquely imply that our eye in the sky masters would lie in order to Tyranically rule over the world...
....but over here in commonsense conservative land we tend to take those placed in charge of pretecting airliners from either being blown up or highjacked and crashed into Skyscrapers.....at their word.