It is more nuanced than that. The passenger said that you hit me like that, I would knock you down. More of a statement regarding how the FA treated the woman than a direct threat to hit him.
Oh please. They were spoken as fighting words not as an academic statement of a counterfactual. And the man rose from his seat angry after saying them. Just as the employee was calling bluff on the passengers threat when he asked to be hit and not making a request for some sado masichism. If you defend the passenger by taking his words literally and out of the threatening context why do you not do the same for the employee...certainly asking to be hit is lierally the opposite of threatening to hit if taken literally? Context and body language and common sense needs to be applied rather than pedantic angles of ratiolization. The passenger was angry at the employee and threatened him. The employee was frustrated and angry back and called out the threat.