If carriers lied to you, they should be held accountable. However, the federal government regulated and controlled the actions airlines were allowed to take for security measures. I know of no government policy that would have authorized private security or even federal air marshals to engage in combat with multiple hijackers in flight.
There was a grand total of 33 air marshals on 9/10. I’m not sure why you thought these guys could cover the “vast majority” of flights, of which there are something like 25,000 to 30,000 per day in the US.
Do you seriously believe that use of airliners as cruise missiles was a “known risk” prior to 9/11? As far as I know, only one person even brought up the possibility, Tom Clancy in one of his novels, and that was a cargo jet flown by a crazed pilot, not a hijacked commercial airliner.
Prior to 9/11 the vast majority of hijacked airliners flew around for a few hours or days and then the passengers were released, more or less unharmed. Don’t you remember all the directions to stay calm and not escalate the situation by opposing the hijackers?
Sounds to me like you are operating from a severe case of hindsight. I have never seen any evidence that an airline, operating within the parameters of federal law at the time, could have done anything to prevent any of the hijackings.