No this is not a logical argument. Banning biking alltogether would even save more lives, so by your logic we should ban biking. This an other studies show, that there is no especial reason to wear a helmet during normal reasonable biking. The risks for your head are not significantly worse than when walking or driving a car. You are free to wear a helmet of your choice at any of those activities, but they are not required by law for any of those.