How can anyone be against the legalization and taxation of hemp/marijuana?

after watching the union or super high me, and doing my own research I don't see how anyone could be against the legalization of something that could not only heal our economy, but on top of that provide so medicinal benefits, and even for the tree huggers it would stop the deforestation as well as release so much oxygen into the atmosphere that it would end the green house effect. We are sitting on top of one of the most beneficial plants in the world if not THE MOST beneficial one that we have, and we refuse to legalize it. And Please No ignorant people telling me about how it's a gateway drug etc etc...Your a waste of my time.