Not sure why you have to point at the members of the Christian religion as the culprit, when there are people of similarly zealous ilk in each and every religion besides Christianity. Certainly, Christianity has the majority stake of religion in the Western world, but this question is a global one, and I don't remember the last time a person was summarily executed for dealing drugs in a Christian country like one might find in Singapore, or their head cut off like one might find in certain Middle Eastern countries, or (again) killed, in certain African countries.

Pointing a finger at a single group is unproductive when the desired outcome is a more comprehensively understanding, less punitive, and essentially more humanitarian solution for what is at issue.

The real disconnect is that the people in power are not held to the same standard as those being sentenced. When was the last time you heard of a prosecuting attorney being drug tested before they could argue in court? What about a judge, or probation/parole/police officer? If there was some transparency in how ubiquitous drug use actually is, one might have some real leverage when seeking to implement more equitable (and therefore less punitive) legislation that provides fairer sentencing guidelines.