Part of the problem is the nature of alcohol, and how it changes perception. Alcohol, by it's nature, makes you less able to correctly assess your own state of mind. We punish drunk driving to help counteract this effect, to change the question from just whether you are capable of driving safely to additionally whether you will get in trouble even if you can, This is useful since your opinion of your ability will most likely be inflated, so we as a society have adopted rules that reduce the influence of ability in the positive decision process.

Now, I agree that the punishment has gotten out of hand. That's likely because it didn't have the impact it was hoped it would have, and so the punishment has been slowly ratcheted up over the decades to try to counteract this. That's an unfortunate side effect, and worth its own conversation as I agree it can literally ruin people's lives, but I think it's a distinct issue from whether drunk driving should be punished at all.

> Is driving after a few drinks really something like 50x more dangerous than blowing through a stop sign at speed?

I'm not sure, but in whatever calculations we make about this, we need to keep in mind a few additional points when considering driving while intoxicated. First, intoxication does not cease when the problem situation starts. That is, a distracted person may notice a pending accident too late to prevent it, but they still have a chance, under full control of their faculties, to try to mitigate the problem. Second, a driver distracted through their own fault may alter that behavior at any point, while an intoxicated person cannot (a person distracted from outside stimuli is not something you can really guard against).