I am always amazed in the post 911 environment, with governments even in the western world democracies running roughshod over civil liberties and introducing rules for one reason and then applying them for another (eg RIPA) to hear intelligent people say 'if you have nothing to hide just trust those decent honest politicians'
As a scientist I would start with the question 'what is the problem?' Is there unrefutable evidence of pilots drinking and causing risk or harm? Of course there is the odd pilot who is caught out, but these isolated mavericks will not be prevented from flying by random testing unless such testing becomes the norm or like in that lovely country India before every flight
There is also the issue of employer:employee relationships. We have looked at random drug testing in hospitals but we know the rare abuser will circumvent the system and the damage to morale will far outweigh any benefit.
And where does it stop? Drug screening? Interviewing the family behind your back? Covert surveillance of suspected pilots? Mental illness is a massive subject and poorly managed in most countries. Greater support and treatment gets my vote any day. but the Germanwings accident had nothing to do with too many beers the night before so please dont use it as an excuse foralcohol testing