This thread is discussing the “Free Palestine, F Zionists” WiFi hotspot and the threat to turn it off within 30 seconds or face the FBI. Which is explicitly not a threat, whereas “BOMB” in the context of a plane is more obviously a potential threat.
I don't see that as necessarily true. I can imagine many situations where F INSERT NAME OF ENTITY would be considered threatening. If they had F the captain of this plane, would the captain be wrong to feel threatened at all?
If someone gets up and yells “F the captain”, it is reasonable to be fearful that they might act on that sentiment, but the statement itself is not a threat; not an expression of intention (or in the former case, presence of an object that is intended) to inflict evil, injury, or damage.
The captain and established protocol follow what has been found to be useful and reasonable when on an aeroplane, not teenagers, jokers, or l33t haxx0rs, and asking people to turn off their bluetooth is reasonable, as is turning a plane around when they won't.
Asking people to turn their Bluetooth off can be reasonable in certain scenarios, like that of the “BOMB” incident. Saying “F <whatever>” is not a threat.