I don't follow you - there were infinite arguments against the seatbelt laws, mostly that the government had no business interfering in my personal decision whether or not to protect myself. I'd say helmet laws, for both motorized and non-motorized two-wheeled vehicles, are exactly analogous. The only person I'm hurting is myself by not using a seatbelt.
Of course, if you are against the government regulating against deleterious health effects, you are also likely opposed to alcohol and cigarette taxes, and certainly criminalization of various drugs.
I'm just not so libertarian. All things equal, helmets save lives, and if you can get people to use them, then all the better.
I'm definitely against the criminalization of drugs. Do you know anyone who wants heroin but can't get it because it's illegal? How about weed? Of course not. All the laws do is make quality control impossible which is what causes most 'overdoses', and when it does happen nobody wants to call an ambulance because they don't want to get in trouble. It's also the reason most violent street gangs exist.
Helmet laws bother people for all the reasons already given to the point that they don't ride bikes. This obviously isn't true of seat belts, Mike's dress shirt wrinkles aside.