There are always those who keep a strong sense of self-control. Would you include them as well? I guess if you use it for that "spiritual connection" sort of idea, I wouldn't see any harm in it. Not that I'm an expert in the field but I always thought of it as broccoli, but for your brain. It's a plant and as we know, green variations of plants are the healthiest for us. Logically, if we put that in our brain via smoke inhalation, wouldn't it have those benefits but applied mentally?
Obviously, you thought of this but it must be mentioned: some plants are poisonous. Some, like coffee beans, may have some benefits but if misapplied, can cause real problems. You've seen someone with a coffee withdrawal headache, right?
To my mind, the benefits of marijuana are not mental as much as they are personality-based. Relaxation, ego-death, contentment with self... these are mental in that the personality is mental, but they replace functions you otherwise need to develop on their own.
This is why generally drug users become dependent. Marijuana isn't bad or good; it's just there. But we need to measure the consequences of its being in our lives, and see what it means -- and what the experiences of others have been. If 90% of them have ended badly, it's of questionable use to us.