Because what is in your blood has an impact on your behaviour, your behaviour has an impact on the people around you. The people around you are members of the society you live in. etc etc.
By that basic premise you are stating, is it ok to drink drive. What is to the government what you do and what you have in your body?
Sorry, but IMO you are looking at this incorrectly.
My
body chemistry does not infringe upon your rights in any way shape or form. My
actions may or may not infringe upon your rights.
And honestly, the problem is not that someone is drinking and driving. The problem occurs if they hit you, etc. THAT is the crime, and should be treated accordingly.
What about bad drivers? What about women drivers ( I kid...I kid...). What about people that just aren't smart?
Should we have IQ tests?
You can't legislate against potential problems, only actual problems. Again....IMO.
Didn't you see Minority Report? (joke, but my point remains).
It is just like the ridiculous argument that crime follows drug use. Well, ok, so prosecute the darn CRIME, not the circumstances that may or may not have anything to do with it. PLENTY of crime follows booze, love, sex, food, and a million other substances/acts/behaviors.
If blood chemistry is involved there are arbitrary lines which must be drawn. I only drive if I have had less than 2 beers (I am not much of a drinker)- but others could probably drive just fine on 4-5 beers (or more).
Either way, the only problem comes when they hit someone, etc. Which is ALREADY a crime.