Also to add, who cares?! Whats walking got to do with cycling? You might as well compare fly fishing, potholing or watching TV. As BenB knows (but daren't admit) its a complete non-sequiter, a logical fallacy, red herring and irrelevence. Forget it. Move on.
It's not. It's illustrative of people's logical inconsistency that they want to promote head protection for one low risk activity, but not for another low risk activity.