Here's the deal. The guys weren't doing anything illegal. Open carry is legal in Virginia, as it is in most states. Most state laws don't cover open carry, ergo, it ain't against the law.
If you go over to the Second Amendment Foundation, you can find a link to all of the state's constitutional provisions concerning the right to bear arms.
The provision of the Louisiana Constitution that I'm familiar with says this:
The right of each citizen to keep and bear arms shall not be abridged, but this provision shall not prevent the passage of laws to prohibit the carrying of weapons concealed on the person.Many states have similar wording.
Open carry is generally legal in the United States. The most common example is when a sportsman carries a rifle or shotgun afield for hunting. Long guns are notoriously hard to conceal. If open carry wasn't legal, we wouldn't be hunting.
In the old days, when state constitutions were being written, most states adopted constitutional provisions that allow citizens to bear arms. Bearing arms means carrying them. Some states adopted provisions that discuss concealed weapons, because at the time, bad guys would conceal weapons for nefarious purposes.
Each state's laws and constitution vary to some degree, so the usual cautions apply. Don't do anything that might be illegal. However, open carry is legal in most states, simply because it isn't forbidden. The vast majority of states make concealed carry illegal, but open carry isn't even discussed.
This all reminds me of a converstation I heard between a rookie officer and a veteral sergeant. It's tranlated for clarity, without the use of police codes, but basically, it went like this.
Rookie: There's a guy carrying a shotgun down Fifth street.
Sergeant: What's he doing with it?
Rookie: Nothing, just carrying it over his shoulder. I'm going to approach him and see what's going on.
Sergeant: You're going to leave him alone. It isn't against the law to carry a shotgun in this state.
Louisiana law talks at length about concealed weapons, but has very little to say about open carry. It is generally not illegal.
I suspect that the officers in Virginia who approached the guys in the pizza joint were fully aware of the prohibitions against concealed carry but were taken aback when confronted with armed men carrying openly enjoying their pizza. Those guys were exercizing a right.
We've all heard the old mantra about physical exercise "Use it or Lose it". The same philosophy applies to rights as well. We should exercise all our rights regularly.