First of all, I don't agree. If this were really all about economics, then appeals to non-economic fears wouldn't work. But Arab terrorists and Mexican rapists aren't coming for your jobs. They're coming for your sons and daughters. Those aren't economic appeals.
They also represent a tiny percentage of the appeals actually being made. Talk to some of these people some time. I have. You don't need some bogus "study" to find out what is driving them. They'll tell you -- and you won't even need to give them a hackneyed question about why black people lag economically to get them to.
Second of all, even if you were right, so what? The source of the racial resentment doesn't change its existence.
Because a pretty significant portion of the resentment in question here isn't ultimately racial in nature. The race factor, for such people, is incidental. Granted, I'm sure plenty of people allow their economic angst regarding immigrants to morph into racial enmity. But, then, I know WWII vets who to this day don't have the first nice thing to say about Japanese people. When I'm around them and they make comments to that end, I have to remind myself that, however illogical I find that perspective to be, no Japanese person ever tried to kill me or my friends.
Truth be told, I'd say that people who feel economically insecure due to tectonic shifts in the labor market should be far more concerned about the impacts of technology, in all of its forms and manifestations, than anything having to do with either trade or immigration. I think it was Tyler Cowen who pointed out once that nearly three times as much job attrition in the past 50 years or so was attributed to technological development rather than outsourcing or anything of that sort. But, then, it's hard to have hard feelings towards robots and computers -- or to shame others for doing so.
Third of all, none of these comments justify your repeated assertion that this research is methodologically flawed. You are complaining about interpretations you disagree with, nothing more.
No, it is not the interpretations I disagree with. If the authors of this farce were truly interested in getting an accurate read on racial resentment, they'd have gone about it in a much different way than they did. As even you acknowledged, they wholly discounted all but one kind of racial resentment. That's not a gripe with their interpretation or conclusions -- it's simply pointing out that they put garbage in and thus got garbage out.
And, while that by itself ought to be enough to discredit this "study", it's just for starters. Their "statements" necessarily required broad racial generalizations and left out all sorts of perfectly legitimate responses that wouldn't fall anywhere on a straight-line "agree/disagree" continuum.
Again, if I believe that anybody -- regardless of race -- could do better than they have if they "try harder" (however I would define that), then it follows that I believe that about any black people who are lagging behind. But I also believe it about any white people (and Asians, Hispanics, Slavs, and Eskimos) who are lagging behind. So, given this is representative of what I believe, how in the hell am I supposed to respond to their question?
If I say that I agree with statement #4, that pushes me toward their "racial resentment" category --
despite the fact that I believe the exact same thing about white people. On the flip side, if I disagree with statement #4, that is not at all an accurate reflection of my beliefs -- because I very much do believe that anybody who isn't doing as well as they want to can do better by way of their own efforts, choices, habits, etc.
As such, I'd probably have to put that I agree with the sentiment -- which makes me (in these numbskulls' eyes, anyway) a racial resenter, despite the fact that my belief about efforts/choices/behaviors and economic success being inextricably linked is entirely race-neutral.
This is the sort of thing that software engineers would call a "bug". My sentiments have nothing to do with race -- but would nonetheless, in the conclusions of the study, make me "racially resentful." And I'm not.
Whatever you might think about that criticism, it ought to at least be clear that I'm taking issue with more than just their interpretations.