Indeed.Well, breaching the peace (as a distinct offense) has been against English common law since the late middle ages. Since before that, it's not been necessary to cause physical harm in order to be arrested and brought to trial.
You're railing against something that's never been okay. You're not responsible for causing fear in others if you're engaging in normal, everyday, reasonable conduct. But this kid went out IN ORDER TO PROVOKE A REACTION. He wasn't doing anything normal. This kid didn't ordinarily get jocked up and go out to Walmart. He did this to see if he could cause a stir, and his wife told him it was a dumb idea.
The issue here isn't so much 2A. If this was just about him carrying, it wouldn't be news, and I doubt the firefighter would have drawn down on a hunter coming into Walmart for a case of Gatorade with his rifle. But this doofus carried in a specific way calculated to cause a reaction, and that's never been okay.
Open carry may be a time honored, legally protected practice (in some states), but let's not fool ourselves here. The law was written when open carrying meant a pistol in a holster or a rifle slung over the shoulder. The trend of tacticool ninjas rollin out into public with their rifle at the low ready is relatively recent. I'm not sure what planet people think we are on where "open carry however the hell you want" is going to be a legally protected right. If lawmakers decide this kind of behavior is a public nuisance, they will end it and it will survive court review. If people keep open carrying rifles into WalMart like it's an active combat zone lawmakers will start making the law much more specific.
Even a SCOTUS from the 2A wet dream is not going to step in and say otherwise.
Photos like the one Queen Bee posted are going to have the caption "how edgelords open carried for that brief period of time before this kind of BS was outlawed" in the future if this trend keeps up.