Gromit - //Of course andy-hughes is talking rubbish. //
Well, I would take issue with your assumption that my argument is invalid as a given, but onwards ...
// The vast majority of people who drink at the airport and on the plane cause no trouble at all. Stopping law abiding people drinking because of one or two idiots would be extremely unfair. //
You could use that argument about drink-drivers, heroin addicts, people who punch people randomly in the street - just because the majority cause no hard doing something does not inherently make that activity desireable.
//Fights and arguments break out amongst sober passengers too, what daft reason would you use for not allowing them to board? //
I don't believe they do actually - and you are clutching at straws to think that an occasional disagreement over space or luggage stowing equates to the full-on violence engendered by putting drunken idiots in a confined space with a rarefied atmosphere, and then feeding them more alcohol - such as this incident referred to in the OP.
//Millions of people travel every year so you will never stop some having disagreements. //
Disagreements no, full-on alcohol-fuelled fights, quite possible.
// Existing laws and fines are successful in keeping this sort of thing rare, and not something that occurs on every flight. //
Statistics would argue with you on that point - it is acknowledged that air-rage incidents are on the rise, and alcohol is routinely at the root of them.
So I think your defence is seriously flawed - but not 'rubbish' - just difficult to maintain in the light of statistics.