But some of them are clearly not qualified to make an informed decision?
Somehow we're OK with airlines violating people's right to freedom of movement (Everyone has the right to leave any country, including his own, and to return to his country.")
It's like trusting medical facility receptionists making a determination whether somebody's needs to be operated or not... Either they need better training or don't burden them with responsibilities they cannot carry out. Either way, just ranting, not really proposing a solution other than knowing your rights and having Carrier Information Guide printed.
To OP: I'd definitely place a complaint and ask airline to train their staff better. Not sure if it would have any effect, but maybe one day somebody will take it seriously.