you just explained one of the driving forces of assimilation of french speaking people.  they have been taught to feel ashamed of their culture and language the minute a unilingual anglo walks into a room.  by constantly accomodating the anglo, who may or may not be a closed minded bigot, they have over time lost their language.  the siblings still speak it among each other in a private setting with no anglos around, but their children do not speak it at all.