I think this is an interesting observation. White, blue collar earnestness has been a fascination of mine over the last few years because 1) it appears to be a class-based (why?); 2) it seems to be a relatively new phenomenon (why?); 3) it seems to play right into the hands of the Republican party (why?)
[WS:] My guess is that the different lies between the real thing and identity politics thing. The real labor had a really tough life and yearned for a better one, one that used to be available only to the upper classes. The identity politics labor (or for that matter, revolutionaries, soldiers, Jews, Muslims, nazis etc.) are basically suburban bubbas and blasé intellectuals who live cushy and boring middle class lives and yearn for something more exotic. Hence thy adopt an _idealized_ version of labor culture (or militarism, or Jewishness, or Islamism, or nazism, etc.), one manufactured for a middle class consumption.
This is akin to the "Irish theme" bars that pop up around the globe - that look "quintessentially Irish" except that they are very much different from the real thing - as our Irish friends on this list can undoubtedly attest. Likewise, identity politics of any stripe (labor, ethnicity, left, right, etc.) is a manufactured consumer product - not a real thing. A product designed to appeal to the consumers' (middle class or blasé intellectuals) desires, pre-conceptions, and expectations. A real Irish bar, which is basically a hole in a wall where the locals meet and socialize, would \not create the right spectator experience to a pampered middle classmen who are yearning for a more appealing and exotic spectacle. Ditto for other identities - identity politics laboristas are more spectacularly "labor" that the real labor, identity politics Jews are spectacularly and ostensibly Jewish, ditto for Muslims (e.g. the battle over the veil in France).
Umberto Eco nicely captured that phenomenon in his 1970s essay "Travels in Hyper-reality" in which he explores the American theme parks. He argues that the essence of these parks is that they are copies of real things that look more real - or hyper-real- than the original for the purpose of enhancing the spectator experience. Today, hyper-reality spilled over form theme parks to almost every aspect of everyday life - anything from housing, bars, and restaurants to identity politics.
To sum it up - the earnestness and "bitchiness" of the "labor" or "blue collar" culture is a manufactured consumer product that fits the hyper-reality model i.e. offers a stylized, enhanced or caricatured version of the real thing in order to better appeal to the middle class tastes, desires, and expectations.
Wojtek