"Nanny State" is a phrase commonly used for government control of people's behavior "for their own good." There are an increasing number of such laws and regulations, and rarely are they of any value. Worse, they usually suck resources which could be more effective elsewhere. Even worse, from a law enforcement perspective, is that they usually are followed by demands from the lawmakers to "push" those new rules, making cops enforce them (and thus taking them away from enforcing legitimate laws and dealing with safety issues).

Gun laws and bicycling are rarely related, and definitely not similar except they are both areas in which those who do not participate attempt to exert control over those who do. Shooting while riding a bicycle is rarely effective, but attempts to do so have generally proven to be a source of amusement for observers.

The bottom line is that helmet laws for adults are not legitimate nor within the powers granted to government by the Constitution, and exist only because they are just a few more among many such laws, which protect each other by being so numerous that they will never reach judicial review.

All of the above said, I wear a helmet when I ride, I promote helmet wear, and I figure that if you have anything that a helmet would protect, you will protect it to the extent which you consider reasonable -- if you're wrong, you're wrong.