I agree with you in some ways, but I don't think the "voting against their self-interests" argument is very strong.
My interests are higher taxes, finding public transportation and public healthcare. In their short-term simple view, I want higher taxes, so I'm the one voting against my self-interests. They live mostly in rural areas which public transportation doesn't serve at all.
Their interests are lower taxes and hating & doing bad things to people in the out-crowd. Again they only view short-term with a limited empathetic view. So they have no empathy for the out-crowd, until they find themselves or a loved one in the out-crowd. This the leopards eat faces, and we such on them for their lack of empathy giving them their due.
I wish we could open their mind to greater empathy and to be more future-thinking, but their brains are broken, I think.