I think these are not so much myths as value statements.

The only trouble these really cause is when the people who hold these values engage in risk-taking to support them.

If motorists didn't overtake too closely, or into the path of oncoming traffic, or too close to junctions when attempting to avoid being slowed, their desire to pass would be of little concern.

If cyclists didn't try to pass other traffic on the right at junctions or in door zones when attempting to avoid being slowed, their desire to pass would be of little concern.

Getting everyone to better understand the reasons behind the basic concepts of first-come, first-served, equal right to the road, and proper destination positioning would reduce these problems. But most of all, a little more patience is needed on the road.