Motorists invented the incompetent cyclist policy, to suit themselves. The balance for this is probably more Republican than Democratic. Then the environmentalists jumped aboard with even more fervor. The balance for this is probably more Democratic than Republican. For further evidence, consider the list of members of the Congressional bicycle caucus posted by Bekologist.

However, none of these people or public need to openly state that their policy is that of cyclist incompetence. They don't need to ever say it, because that taboo is so ingrained into the America psyche that the only time it becomes obvious is when a few persons maintain that cyclists can be competent to operate in traffic according to the rules of the road for drivers of vehicles. In short, the incompetent cyclist taboo and policy becomes visible only when it is contrasted against the opposite view.