I did answer the question in context. If you are asking the question without any context, no assumptions can be made, certainly none that would justify shooting a passenger to death.
In context, Alpizar's wife identified him as her husband, and told the marshals that he was sick. In context, an appropriate assumption was that Alpizar was sick and needed to get off the plane.
And you can keep your "logic lesson," with your "logic" we would see hundreds of shootings in planes and airports annually; fortunately most air marshals are using at least some common sense, and not Raycpa "logic."
(and BTW, it's interesting that the pro-kill posters don't refer to Alpizar by name.)
The context is the training of the marshalls. Again what assumption do you think should be made when someone disembarks from a plane while leaving their checked baggage behind.
(I thought I would at least have to make three moves to put you in checkmate, but I didn't expect you to fold)