I think a reasonable adult will conclude that it's anything but obvious that bicycle helmets are effective in reducing serious head injuries. Unfortunately the debate is a little more complicated than the level of the treehugger article, but it's worth the time if you're actually going to bother to hold an opinion on the subject and take the trouble to express it publicly.
I think a reasonable adult could come to an entirely different conclusion based on the preponderance of evidence. For example, this is
rather sobering. But I don't think slapping the anti-helmet crowd in the face with statistics like this will change the closed minds here one single bit as long as there are a few contrarian studies to cling to. Much like climate-change deniers.