Goodness....Everyone has to have a cause. Tell your mom to teach the kids some manners...or etiquette...or basic human decency.
Isn't it reasonable to instill some social mores with the kids? Expectations that are consistent with OUR society and culture. Nobody should have to debate whether or not your mom is being insensitive to the one child in the school who might, twenty years from now, travel to a distant land and have a meal.
I guess if we can't teach them EVERYONE's minutia/agenda... then we're better off teaching them nothing at all?? What, exactly, is the social workers suggestion here?