And still people seem to have their heads in the sand.
You don't resign if you are not guilty. You use the not-inconsiderable legal resources available to you through BALPA and you fight.
The fact that BA were clearly going to terminate them with no compensation, and that they didn't put up any fight at all, tells you all you need to know. They clearly accepted that they were guilty, and the subsequent events indicate that they accepted that they were guilty of a lot more than having trace amounts of alcohol in their bloodstream in a zero-tolerance country.
I feel sorry for them personally,, but frankly the industry is better off without people who have such poor professional judgement.