I mean, in the case of alcohol, it will always be my stance that never, under any circumstances, will I drive after knocking back a few; or even one or two (yeah, I'm only 18, call the police).
This is all well and good.
The problems start when you try to enforce zero tolerance with a law; instead of getting everyone to drive totally sober, you'll get people driving in various states of intoxication simply because they won't even try to follow a law that is totally unreasonable.
There are lots of people, me included, who drink beer at meals. I intend to drive now and in the future too - regardless of the law - after the one or two beers I drink with my meal
(for my bodyweight three is almost exactly at the limit, I don't really even notice any effect from two). Then there are for example people from Southern Europe, who really like using wine with food and the almost stereotypical Germans with their beer.
And people who just like to occasionally eat for example business meals at restaurants;
usually these meals do include alcohol.
With a zero tolerance by law you would require all these people to change their habits, or just ignore the law. Which one do you think they'll pick?
While the goal might be admirable, one is better off by setting a goals that are actually attainable, instead of the ones that would be "just great".
That of course has nothing to do with
your personal choices, and if you want to use zero tolerance with yourself, that's great.