This would be fine if the limit was set low enough that it didn't allow anyone to drink enough to increase their chance of an accident by 400%. But it isn't.
The whole reason for legislating against drink driving is based on the causational link between drinking alcohol and diminishing driving ability, yet the limit is set at one single level for everybody and for a significant number of people that level is WAY too high.
To back this up, i've had two pints before now and been well under the drink drive limit (used one of those miniature test devices you can get). Didn't drive, for the record. Clearly i'd have been impacted for driving though.