What about over the counter cold medications? Slows your reflexes, makes you drowsy. What if you have or are recovering from flu/cold? You are impaired far more than having a beer.
I carry primarily for self protection and to exercise my right. My primary goal is not to educate the public.
What if I'm sitting in a bar with friends, sidearm on my belt, sipping a club soda? Am I to be concerned with what some refugee from CA sitting at the next table perceives?
As 28Kfps and Dirty Harry says " you got to know your limitations ".
TBG
If you carry for self protection then I'd think open carry is not a great tactical idea when drinking alcohol in a bar. As discussed already, booze slows you down -- even 0.03 BAC is enough to start impairing judgement (ability to rapidly assess a situation and respond properly) and fine motor skills; the effects are measureable even if people don't "feel" drunk.
Moreover, bars tend to be crowded and full of drunk people. Open carrying in such a situation sounds like a serious retention problem. How confident are you in your gear? How much unarmed weapon retention training have you had? Do you have a non-lethal option available (baton, spray, taser, etc) in the event that a drunk starts something that is short of a "shooting offense" (i.e. fear of death or grievous bodily injury)? If you have to shoot, have you had sufficient training to fire from retention (or speed rock, or whatever your training dictates) at extremely close quarters without hitting bystanders?
Based on the reflexes issue and the retention problem set, based on my level of training, if my primary objective was self-defense then I would choose to cover up and not drink.
If your objective is to publicly exercise the right then that is different. In that case "flaunt it" all you want. However, I would argue that if you want to exercise the right then there is a responsibility that goes with that. Whether we like it or not, when we OC we are ambassadors and representatives for the 2A. Context matters. I'm not saying that it would ALWAYS be appropriate to cover up in a place that serves booze; but one an see how there might be certain appearances that do more harm than good. There's a lot of gray area between "discreetly carrying a black sidearm in black holster against black shirt and drinking an obviously non-alcoholic drink quietly in the corner" and "boozing it up boisterously with a Rossi Ranch Hand or Draco AK strapped to your leg."
I personally cover it up in crowded areas full of rambunctious people that would pose a retention or escalation issue. I don't drink when carrying open or concealed unless I'm having a REALLY good steak that deserves a single glass of wine, or a dessert that deserves a single glass of port. I do appreciate that it is legal to do so and think that it should remain legal, having been in states where drinking while carrying is not allowed at all, but still don't think it is a great idea. If I ever have to use my sidearm in self-defense I want to be able to say, "No sir!" when asked if I've been drinking.
