This is the original paper in which he makes the comparison
http://jop.sagepub.com/cgi/reprint/23/1/3

He reports that ecstasy use causes acute harm on average in one-in-10,000 cases, whereas horseriding causes acute harm in one-in-350 cases. Yet the former is illegal while the latter is legal.

Maybe it is a crass and insensitive comparison, but it makes the point that public policy must be based on evidence – not personal preference and reaction to daily news headlines.

Then there is also the problem of enforcability of the law. If you can't enforce it consistently because the behaviour is too widespread then the cost of prosecuting it is a complete waste. 730,000 regular ecstasy users? there are only 85,000 people in prison – are you prepared to pay the tax rise required to make the clampdown? Or do you propose laws should be ignored?

If the law fails to deal with practical issues, the people who make and uphold it will begin to be held in contempt as officials lose authority over what they do. Worse is the way in which such behaviour patterns don't happen in isolation, and when more serious issues are at stake the consequences are starker.

The culture of setting policy according to whim and not according to proper consideration of the evidence lay at the heart of the decision to invade Iraq, the deregulation of the banking sector and the setting of the expenses rules to give three simple examples.

In each case contendious justification was provided for undertaking the policy, implementation hadn't be fully considered and adequate resources weren't made available.

Yes Saddam was a bad man, companies want higher profits and politicians need to be in contact with ordinary people, but the way each matter was handled was flawed by lack of scrutiny of the evidence, and we are paying through the nose for the consequences.

Do we want more of that?