In just the same way that I've been called a Toubab. It literally means 'black' but if used in a jeering way can be a bit cheeky and rude. I've had little boys in Senegal grinning and calling out "Toubab! Toubab!" But honestly, if one is as sensitive as all that and takes offence at silly stuff, one should stay indoors and watch daytime TV. I must add that I too have been called a Sassenach in Scotland, and it was in fact out of prejudice against 'The English'. But when one considers Scottish History, it's a wonder they even let me into their country at all!