For me, it’s occasionally coming up when I listen to comedians. A year back I also heard a story about a white person who grew up poor, became financially stable with a good job, and then punched down and started calling other white people “white trash.”
To me it’s obvious this is poor-shaming. But I have a feeling it’s far more complex than that. I’m not even white and I feel degraded whenever I come across those words. I barely know what it means, but it breaks my heart anyways to hear.
Maybe a more general way to think about it is that white supremacy requires a certain positive characterization of whiteness as a high class, virtuous, cultured, and refined identity. When that fails to align with reality, the people who are counterexamples are called “white trash” to distinguish from classy whites.
Best illustration is 2 white supremacists, one conservative and one liberal, talking, when the conservative starts ranting about how rowdy and criminal the minorities are; the liberal argues back “it’s not just the minorities who are like that, there’s white trash too” i.e. white people can also be nonwhite!