Don't be ridiculous. It is an absurd situation that is completely their own fault and falling back on 'its our plane, we make the rules' is a direct contradiction of every statement they make with regard to customer service. Its dishonest, lazy and piss-poor conduct.
They may well have the right to do it but that is a right they shouldn't be exercising, and certainly not in this manner.
****s. Worse than BA and that is saying something.