people who live in a mobile home
Since I have relatives that have lived in mobile homes, I live in a home in Mobile and I had an uncle that owned a mobile home dealership, I can hardly be prejudiced against them.
In the South, "white trash" implies much more than living in a mobile home. It implies lack of grace, abject ignorance, incest, bestiality and total lack of moral fiber. The mobile home is optional. We joke about it among ourselves but nobody calls someone "white trash" without a big smile on their face.
I don't even know if Matt is from the South so he may not have the same perception. In which case, this all becomes little more than a discussion of Southern culture.