Generally bigger people have more blood/body fat, which is why more beers = less drunk = blow less on the breathalyzer.
Generally alcoholics process alcohol faster, so again, more beer = less drunk = blow less on the breathalyzer.
The breathalyzer is supposed to overcome the issue of different people consuming different amounts of alcohol leading to different drunkenness.
The reason why the law is a hard scientific line as opposed to how sober someone acts is largely because when drunk, a person's judgement is impaired. They may think they're acting more sober than they really are (who hasn't felt this way?).
Finally, most people who get behind the wheel drunk have no intention of injuring someone either. People most likely WERE in just as much danger as when Kidd drove, JV just didn't happen to hit anyone/anything.
Having said all this, I'm a firm believer that all issues should be handled legally, and I'm not advocating for the franchise to impose any additional consequences above and beyond those stated in the CBA.