Remember kids... always wear a helmet. (The almighty bikeradar helmet thread)

But I am sorry, anyone with any decency will make it damn clear that despite this helmets are 100% a symptom of the problem and 0% part of the problem. The closest parallel I can think of is that anyone with any decency will say that a young women who wears little clothing, gets blind drunk and gets into an illegal minicab late at night and ends up a victim of a sexual assault is 0% to blame despite the fact that with hindsight we can all make suggestions to her as to how she might have behaved differently to reduce her chances of becoming a victim.

Logic 101 says you can't prove anything by analogy. It's a poor analogy anyway: you are trying to show the difference between cause and symptom but your analogy actually demonstrates the difference between causation and negligence. It's not wrong but it doesn't illustrate your symptom/cause dichotomy. (And that in itself is a false dichotomy: http://en.wikipedia.org/wiki/Positive_feedback)

Also, that's the second time you have used a rape analogy. It's pretty gross that this is your go-to image, and hideously ironic that you started that paragraph with the phrase "anyone with any decency"

If helmet wearing is a "symptom" of the problems caused by cars, the analogous "symptom" in your little rape scenario is not the woman's choices but the rape itself. You are apparently saying having to wear a helmet is analogous to being raped by cars. It's a brave position, I'll give you that.

We have a duty to accept the reality - that fewer helmets would reduce 3rd parties impression of cycling being dangerous [edit - and it might well be good !overall if fewer people wore them]. But as important if not more important is that we have a duty to remember that people wearing helmets is not the problem on any level whatsoever - bad drivers, bad cyclists and ignorance are the problems.

The reality is that humans learn from other humans, so in the absense of more formal information about safe cycling they will look at the cyclists in helmets, see that the majority choose to wear them, assume they must therefore be necessary and follow their lead. So because it is the most visible step a cyclist can take towards safety, the perception grows that a helmet is the most important step towards cycling safely. And this is compounded by the well meaning advice of those who say "well it must do something" or "if it makes even a tiny difference", and by the less well meaning advice of organisations like the AA who choose to promote helmet use rather than address much more significant risks to cyclists.

Now you will undoubtably say the problem is not the helmet but the ignorance and assumptions being made. And in principle you would be right. But that is basically staying the problem is we have the wrong sort of people, because humans are wired to learn by example. And trying to solve a problem by changing the people to meet the principle never works.

So here's a better analogy. Wearing a helmet is very often like the drunk looking for his door keys under the lampost instead of by the door where he dropped them. It makes him feel like he's addressing the problem but he isn't, and it's stopping him doing anything to solve the real problem. Initial cause: dropping keys. Ongoing cause: trying to solve dropped keys with the wrong method.