Why is it slander to note that Wegee was an artist and was perfectly capable of making his own statements -- and in fact was known to have staged photos at times, as any photographer does? Unless Wegee himself stated that this one was documentary rather than artistic, there's no good reason to believe it has to be one or the other.
The camera always lies -- if in no other way, by capturing only a small piece of what's going on, at a specific instant, selected to reflect the photographer's ideas of what's interesting and/or meaningful. Further lies generally occur in the darkroom as it is cropped and burnt-in and otherwise adjusted to clarify the photographer's intent.
A good photographer uses those lies to make statements, and often those statements are truths -- but they don't have to be, and sometimes the truths are figurative rather than literal. There's absolutely nothing wrong with that. But it does mean you need to know where and when and how a photo was taken before you can be sure of what you're seeing.
If Weeee said this was reportage, I'll believe it -- but that statement would probably also explain why this situation arose. Without that statement, it seems so blatently unlikely that I have to believe that someone (NOT Wegee himself) has misdescribed it, and that it was a created scene -- whether for the photo, or from a dramatic production, or a protest, or whatever. Note that some of these would make it a wholly legitimate piece of photojournalism, but would invalidate the description we have of it.