Good point, our 'culture of rage' is a tough nut to crack; and it's much larger than this niche subject of accepting a person riding a bike on the road. Hell, driving a car these days, I often get other drivers make threatening maneuvers ... but in my car, I have a seat belt, air bag, crumple zones, etc.
In a related note, we are not jerks to every person on the road that isn't in a car - over the Thanksgiving weekend we had a series of snow systems drop more than a foot of snow. The city was having a hard time keeping up with the snow and had little time to get back to some of the sidewalk ramps. We saw a person using a mobility scooter force to use the road because the sidewalk ramp wasn't cleared. All the drivers gave this person lots of room.