Real logic would demand valid reasons for adopting a behavior (since we are born without helmets that is the initial state). That is, it is the burden of those who wish to change the initial state (helmet-less) to prove their point (helmet use).

Again, motorcycles are so vastly different in so many ways that using those studies to justify anything in cycling is absurd. For example, motorcycle helmets with their increased protection (as compared to cycling helmets) while defending a human head in a much more dangerous activity justifies their personal adoption while the public-born financial costs associated with motorcycle accidents justifies their mandatory use. Cycling isn't nearly as dangerous as motorcycling nor are the helmets nearly as protective. The public cost of the treatment of cycling injuries (the ones helmets could prevent) could probably be covered by the amount we spend on helmets themselves. The differences between motorcycles are bicycles are vast as are the difference between their corresponding helmets. Arguments for either one do not prove or disproves the other's case.

I often feel that the helmet zealots need to justify their hefty expenditures and their wholehearted acceptance of helmet industry propaganda (all writing is propaganda for something) while refusing to seriously question the source of their convictions. It would be a scary world indeed, if we all just readily accepted advertising as "truth."