Poor analogy based on nothing but numbers, which any scientist should know is rubbish. The type of risk and ability to manage it are totally different.
None of us would deny that horse riding is a dangerous sport. However, good riders try to manage and reduce that risk wherever reasonably possible - e.g. by wearing a helmet, assigning horses suitable to a rider's skills, and learning how to deal with a spooky or bolting horse. Drug dealers do not present the chemical content of their drugs in a clear form so that you can make a fully informed choice about getting high.
With regards to the comments about wasting money, though - I haven't read the study, but I doubt its brief was 'find out if ecstasy is more or less dangerous than horse riding'. I imagine that's just a comment the scientist has made in his discussion, and that the actual brief was something far more valuable, like investigating the effects and dangers of the drug.
If you believe everything you read, better not read.