I agree that the actual ragers are rare; I probably encounter one every two months or so (which is still too many, mind you).
However, I have no doubt that there is a majority of motorists who really do believe that the roads are for them, and that cyclists are invaders who are merely tolerated and are not proper "road users". I believe that this results in motorists taking less care than they should. This is clearly evidenced by the number of drivers who will share the lane with a cyclist whom they are overtaking even when there is an empty lane to their right on a two lane carriageway.
I also think this results in an attitude among some motorists whereby they feel it is appropriate to pass cyclists at an uncomfortably close distance, but which they feel is not actually dangerous, in order to punish them for doing something they disagree with, such as claiming the lane. I probably see this two or three times a month.
It is possible that this general attitude provides a context in which the extreme examples feel their actions are supported, having the effect of moving the "bell-curve" down towards the bad attitude end of the scale. So, any improvement in that general attitude would make our commuting experience better.