The problem with the whole blood/alcohol issue is that we've gone from a somewhat science-based approach to a trend towards 'zero tolerance' or something similar. Much like the anti-tobacco types (full disclosure - I quit 30 years ago) who behave as if they are on a mission from God, so too with the anti-alcohol types.
When the blood alcohol limits for driving were first set, there was some science behind the 0.01% adopted in many jurisdictions. That was the level at which the average person's reactions were affected enough that a reasonable person would conclude that they should not be driving. Some jurisdictions - such as Canada - decided to add a margin of error, and adopted 0.08% as the limit.
What's happened since is that the science has to a certain extent improved and to a certain extent been disregarded. Views based on some sort of moral calculus have come into play - "if you drink, don't drive" and the like. So acceptable limits have been coming down, and eventually, it will likely be illegal to drive with any alcohol in the blood. Is that a good thing? Well, like most things, it depends.
Studies have shown that below about 0.05, there is no demonstrable effect on people's driving. So if you were to test two people in the same simulator, side by side, one with a blood alcohol of 0.05% and the other completely sober, you would not be able to tell from the driving which is which. Where a demonstrable effect has been shown, it's often the other way - that is, people who've had a drink or two, but not enough to be impaired, tend to drive more carefully than those who have not had anything to drink. Between 0.05% and 0.08%, the science now demonstrates some degree of impairment, but whether it is enough to impact driving, or whether it impacts factors which are critical to driving, is still unresolved. Still, it could be considered a case of better safe than sorry at that level. No such argument can be made below 0.05%.
Is is right to criminalize people who have done "nothing wrong" in the sense of not putting themselves or anyone else at greater risk that other drivers? I'd suggest not, but I might be in a minority.