I know you don't want to so argue, but logic is a harsh mistress: if you argue for maintaining a current ban on the basis of accident rates, that argument applies just as well to consideration of new bans.
some means of quantitatively determining whether that limit had been surpassed would be necessary to enforce that limit, otherwise the determination would fall solely at the discretion of the arresting officer, a situation which would not be agreeable to anyone with a sense of 'due process'.
I disagree; walking a line and other 'subjective' tests are fine by me if nothing better exists.
Alcohol has been legal for the entire lifespan of a majority of Americans, Marijuana has not.
So? There was a time when slavery had been legal for the entire lifespan of a majority of Americans; was that a good reason to maintain that policy?
WTF does slavery have to do with operating a motor vehicle?
It's a testing ground for your implied principle that a long period of legality is in itself grounds for continued legality.
But still, nobody has answers with a clear answer : does alcool impairs a driver more than marijuana does? yes or no... nobody answered as clearly, so that means something to me, people can't talk objectively of a subject that would go against their fondamental beliefs, which belief is not necesseraly controled by themself...