The stereotype is right, except for the "rich" part. And it's mostly applied to "porteños", the inhabitants of Buenos Aires. Natives from provinces can get a "pass" in short time.
Granted, whenever I had any sort of conversation with someone from Paraguay I had trouble to differentiate their language from someone from the Argentine northeast unless they started using some Guarani words (and that is still not that useful given it is also spoken in the Corrientes province)