A blanket ban, particularly a 'life-time' ban, should only be imposed by the courts.
A life-time ban is completely inappropriate. No other crime has that penalty.
If they really want to address this issue they should be asking themselves why passengers 'pre-load' with alcohol and try and address that. Banning them after the fact is no deterrent .
Amend their conditions of carriage to provide that they will not board any passenger who blows above a certain breathalyser level. And then do random checks, with emphasis on problem flights. Off load a few pax, immediate media storm, free publicity. But enforcement of their rules must be seen to be effective.