Well... i dont know if i can say im Christhian... i was born and raised Christian, but then i left my parents house, and didnt went to the church anymore. In the meanwhile, i started to learn about oriental religions, mainly buddhism, and also the way of the knowledge (don Juan teachings), so now im a complex mix of many religions.
But i try to merge them as nicely as possible, so for anybody that looks at me from the outside, would say im very Christian... what is partially true. Im Christian, but not only Christian.
And i dont think the act of smoking weed is a sin. The sin is what you do while stoned. If you smoke and do wrong things, the wrong things you did are the sin, not the fact of smoking itself.
But for me weed always was a great help for the spirituality. After i started to smoke, i became a FAR more spiritual person. So, for me, weed is a God's gift, to allow we poor humans to get closer to Him and His knowledge and wisdom.