Are you familiar with the concept of "analogy"
?
black:white::up:down does not imply white=down.
That's a bad analogy for this situation. Lowering a human sense is not the same as having less of a reaction time to avoid an accident. Also, there is a rediculous difference between the safety of a seat belt and helmet.
Let's just say if you're going to do it, go over the speedlimit or wear a headphone, be reasonable.