Maybe I do make a little distinction between the kind of abrasive leftism (and manipulative messaging in the writing styles) of the Hollywood Ten types and the earlier homegrown populist-tinged material. Sort of the difference between downright offensive propagandistic crap like “Salt of the Earth” versus the mild populism often found in 1930s Gene Autry films. Overall, when I get the whiff of a soapbox, I get really annoyed at a film, whether it’s some obviously devised undercurrent, like in “Force of Evil,” which equated capitalism with criminality, or even in “The Ox-Bow Incident,” with its somewhat less-political anti-vigilante theme. Maybe what it is that gets under my skin is when I sense a film being deliberately designed to push a “message” (propaganda) and thus sublimating characterization and narrative, versus a film that might just be telling a story that might come from a left/populist mindset but isn’t concerned with messaging.
There were also a tiny handful of specifically anti-commie items in the 1930s, like “Red Salute” and “Soak the Rich.” Both came on the USA network in the early-1980s. I taped the former, and still have it around here somewhere. Interesting stuff. Then, there were lots of little obscurities like “Gun Smoke” (1931), an oddball modern-day western with Richard Arlen, which would give libs the vapors with some of its sentiments. A good number of films like that from back then.
All art has a ‘message’.
I've seen quite a few "lefty"/Socialistic early movies, through the years as well as some eyeopening precode liberal ones as well. There were also many more proAmerican/capitalist ones that I've also seen, but MESSAGE movies are as old as movies themselves.
As a matter of fact, there have been SO many movies made with "triggers"/"microaggression" that seeing them would burst the poor little snowflake millennials heads would burst!