Let's disassemble the assumptions and biases here. First this assumes that these two people have any intent at all. They may simply have been walking down the street. This isn't likely the case, but I'll cover that shortly. Next, it assumes they are cowards, and that only armed services members and veterans can be brave, or defend themselves or their country. Since the second amendment was born out of the fact that non military people armed themselves to liberate us from the British, this is especially off base. Lastly the assumption that they are "playing army". Because one cannot possibly be engaging in any activity with a firearm, unless you are acting immature. This is an assumption feeding a confirmation bias and back.
The first assumption is the funniest. Ever run into armed people just wandering around? Me neither. That is because it doesn't happen, in this country, unless you are out hunting. This was most likely from one of the many "Open Carry" events in places like Texas, which were to highlight the absurdity of the laws there. It was lawful to carry a rifle openly, or a handgun concealed, but not a handgun where it could be seen. This left enforcement far too open to interpretation.
These protests worked, and as of this January it became legal to carry a handgun openly. Other protests seek to "desensitize" people to the sight of a firearm, which should be no more alarming than the presence of a bat, hammer, or other tool. At no point, that I could find, was the intent of these protests to intimidate anyone. That is why the rifles are slung, and not carried.
I have prepared an image as a rebuttal, which is every bit as ignorant, assumptive, and reinforcing of bias. It was done for satire, and not because I am stating the contained words to be truth.