Is snowboarding dying? Let's hope so.
I can't say ALL of my experiences with snowboarders on the slopes have been bad, because maybe one time one interacted with me while my back was turned (although that's usually when they run you over). And there's nothing magical about skis that can make a jerk be considerate. Yet it happens that skiers are more considerate than snowboarders.
The causation probably runs the other way, where your natural aptitude for consideration of others makes you less likely to choose the less-considerate recreational option. Snowboards don't make jerks, they just allow them to come out of the cities.