I’m not defending the right of people to get stoned. I’m defending the right of people to make decisions about their life that do not affect someone else. If they want to use their rights to get stoned, so be it. The only negative effect you can come up with is “it turns them into leftists”. That is not enough to ban something. It isn’t even in reality enough to make it immoral.
At the same time, if you want to spend your time telling people what the right choice in their life is and evangelizing the right on and moral path on pornography and marijuana fine. Go for it. In the private sector. If you can convince them that your viewpoint is the correct one without government coercion more power to you. However, pornography and marijuana’s negative effects on society are so hard to pin down that banning either one is unjustified.
Nothing happens in a vacuum. No man is an island. Every decision everyone makes affects someone else in some way or another. You're wanting to make smoking dope legal makes it more difficult to teach my children and grandchildren that drugs are harmful and destructive. You're wanting to make pot legal means that pot is going to be more available to the detriment of our culture. It's not a matter of personal freedom. It's a matter of personal responsibility and consideration to others around you. It's about selfishness versus sacrifice.