I agree with you about rights. Who's rights take priority? The riders out there riding according to the laws of the land or those riding under the influence? The question of them being legally impaired under today's definition is kind of irrelevant considering each person reacts to alcohol and drugs differently. While the person may not be legally impaired they may not be in a position to operate a vehicle capable of going from zero to stupid fast in no time flat.
With our rights in this country come responsibilities. It is up to us, as citizens, to follow the laws of the land or accept the penalties (without snivelling). If there weren't issues with impaired driving the police wouldn't be asking people to blow. The recent legalization of weed brings another angle to this issue.
Wether being asked to blow into a breathalyzer constitutes a denial of our rights remains for the courts to decide.