As someone who read "The Scarlet Letter" in highschool, the lesson I learned is that the state really should avoid encouraging and supporting a culture of vigilantism and ostrization. I for one don't think that lasting punishment* for life are appropriate where addiction is likely the root cause. But if the goal is just that, the laws should be changed to do so more deliberately, rather than offload the dirty work to the public.
Also, I can't decide if "whiskey plates" are useful in any real way. As something that is socially stigmatizing, it's really unclear what the social response (if anything) is supposed to be. That said, I don't know of any PSA or public decree what went along with the launch of such programs. Now I'm just curious.
Hilariously, in Virginia, there are "Gadsden flag" ("don't tread on me") plates that can resemble whiskey plates from other states. So, across state lines, you have people inadvertently diluting this "DUI driver on board" message all while expressing a confused mess of other sentiments.
(* I should clarify this by saying that I'm all for one-time penalties for doing the wrong thing, including removing privileges. It's where we brush up against a person's rights, forever, that I take issue with. To me, revoking a driver's license for life is okay, but removing their sense of personal safety and autonomy through crowdsourced abuse, is not.)