Going from "we don't use as much coke as in the 80's" to "the war on drugs worked" is a bit like going from "we have less teen pregnancy now than in the 90s" to "abstinence worked". It's not only ignoring a very large number of alternate factors, but it's assuming the latter is a successful strategy, when all of the evidence points to the contrary.
Because proving causation is always difficult if not impossible? Or because in both cases we have a personal bias that makes us not want those programs to have worked, despite not being able to disprove causation either?
Because in neither case has anyone actually even made a coherent argument for a causal effect that doesn't ignore all the other factors?
Besides, when "all the evidence points to the contrary" is usually a bad sign...
There are a lot of things you aren't able to disprove that are (probably) not true.
