The term "white trash" denotes a socioeconomic class with distinctive cultural affectations stemming from having grown up in a very poor rural environment. The term is also regularly used as an insult against people not of that class, because it is viewed as such a low status thing to be. You can be educated and well-behaved and still unambiguously be white trash, and commonly referred to as such by other people both descriptively and pejoratively. It isn't a choice per se.

People who leave that environment are often very conscious that they are discriminated against for having the affectations of that class and try to erase them. Many people who grew up as white trash will self-identify as such in certain contexts, even if they no longer are, because it accurately conveys the socioeconomic class they came from and are not ashamed of it per se though people may treat them poorly for it.

I grew up as the platonic ideal of white trash. No one can tell today and people are surprised if they find out. When I travel into that environment I can still code switch.