"...being stone cold sober is no guarantee of being safe,I could be killed by a perfectly sober driver talking on [his/her mobile] phone,or who falls asleep at the wheel through tiredness,or who just has too much [testosterone],and thinks he is a racing driver."

But being stone-cold sober does mean that you will have a faster reaction time when trying to avoid an accident with another driver who is doing one or more of those things.

Have you ever had anyone videotape you after you've had your "two pints of beer at 3.8 percent" over the course of two hours? Y'know -- recording your steadiness on your feet, your reaction time to a surprise such as someone jumping in front of you, your ability to get in a car and get the key in the ignition switch, etc.? Anyone ever tape your driving when you've had that much to drink, and show you the tape? If not, then how do you know you're OK to drive? Once your judgment has been clouded by the alcohol, you are by definition NOT the best judge of your fitness to operate a coupla tons of motor vehicle safely.