If God created all plants to be used..?

God said in the beginning that we can use all plants and their fruit except for the tree in the middle of the garden which no longer exists. Therefore cannabis is one of those plants that God deemed usable so to speak. Why do some people insist on saying that smoking cannabis is sinful? Yeah it clouds your mind or whatever you want to say about it not making you think clearly but I find it helps me to appreciate the world around me and all that God has done for us. How can people consider it sinful?