I think everywhere it's a bit similar. There are always be sub races or mix race that never be 100% local or native. and wherever some poor or not well developed regions start to receive some visitor, not as tourist but more like working resident, permanently or temporary, those visitors will always be viewed as walking ATM machine.
For people who like me, who have spent almost a decade in remote area for working at construction site, being in disputes with "homegrown natives" is like everyday routines.
Till this day, I have never held grudges against them. I know those people were not bad, they were nice and good. it's just that they lived in a system that indoctrinated them to believe that belief.
same case with your friends, they could not be changed. All you could wish is that the next generation would not favor that belief anymore.
RE: How is difficult being from different groups in Brazil.