Actually "most" folks don't refer to them as "spiritual drugs," they refer to them as psychedelics and for those of us who really know what we are talking about, they are more frequently referred to as entheogens. You're piece is interesting, always nice to hear what folks think. As a former psychonaut myself I have learned patience and tolerance for the opinions of others, no matter how assumptive they may be. At the end of the day, so much of it is choice. Personally, I would never CHOOSE to limit my own experience. 
At the same time, I have seen people fall into these experiences because it has become trendy and often those types miss the point as well. 
I have often used that Hitchens quote myself, and you are correct, I cannot prove my experiences to anyone. One apparent difference between us is that I would never feel the need to. It begs the question, why are some folks so keen on trying to prove the opposite? Can you prove that people claiming to have a spiritual experience didn't have one? Evidence presented against these claims is flimsy at best and ridiculous at worst and at the end of the day prove nothing. Respect to you and to your opinions however, we are all entitled to them.