It's plausible because there are many people out there who don't view minorities as "Americans." They think those people are not good enough. You still see it today;
Mexicans are taking our jobs. Muslims should be banned. Hispanics can't be good judges. I couldn't go to college because of Affirmative Action. Make America great again. The list goes on and on, and they are all codes for racism. It happens in the Hmong community, too, in both directions. You see people insulting others as closed-minded, primitive, and ignorant. The reality is that they are those things because they simply don't realize that it's simply a different lifestyle without a right or wrong. But, some people will think that all things fall apart regardless, just ask Okonkwo.
That being said, a lot of racists are not just "trailer folks." And, it is not fair to say that a lot of them are racist. We shouldn't assume everyone is a racist by what little information we have; maybe they just want a little help cleaning up their mess. Instead of accusing them of being racist, just give them a napkin.
Racism is often the result of some form of ignorance, and economics tend to affect education.