Big thinkers tend to live in wealthy, leafy areas where they don't have to worry about someone jumping over their fence, or appreciate the need for demarcation of land.
Same goes for people who are pro-immigration/pro-drugs/pro-construction - but just don't do it their affluent area.
These same folks went on to figure out the logistics of preparing food. So no, I don't think it's at all axiomatic that the people who disagree with nationalism are necessarily affluent in the slightest. In fact, I've found most solidarity with refugees and anti-nationalist movements in the working class. The overall community of folks I saw ranged across income brackets -- plenty of software engineers, tech folks, trades folks, unemployed folks...
I think that when people say, "They don't really mean it" or "their principles wouldn't stand up if it meant a disruption to their lives", they are not aware of just how much work folks are actively doing every day to live by those principles and invite people in.