As far as I'm concerned, there are no sides to the argument. It is not a dangerous drug and it does not have long term negative effects and it certainly isn't a gateway drug, because there is no such thing. While it's true that the body can become dependant on certain substances, that dependence is physical and illicit drugs are far from the only thing that can affect the body in that manner. The addiction is mental and it isn't the substance that's addictive, it's the personality. People who have addictive personalities will become addicted to anything that relieves their stress and brings them closer to a sense of happiness.
The best description I've heard of addiction is as follows. Let's say "normal" happiness is 100 on a scale of 0-200. A person who has a happiness level of 100 can use a drug and reach a level of 140. A person who has a happiness level of 60 can use the same drug in the same amount and reach a normal happiness level. The thing is that when the normally happy person comes off the drug, his happiness level falls to normal, while the other person's happiness level falls back to a negative happiness level. The first person will not become addicted, while the second person will. For more information on this phenomena, I recommend reading "In the Realm of Hungry Ghosts - Close Encounters with Addiction" by Dr. Gabor Mate.
As for the legal status of marijuana, I'm not so arrogant as to profess to know how other people should live their lives. But I do know that I live in a nation that treats its citizens like chattel slaves. The US imprisons a greater percentage of its population than any other nation in the history of humanity. We have more peaceful and non violent individuals in prison or under the supervision of the state than any other current nation has actual violent prisoners and yet we still profess to be a civilized nation. I say hogwash. That's not security, it's barbarism and frankly, it's an embarrassment.
To save going off on too much of a rant here I'll close with this... I think everyone who wants to use drugs (of any kind) should be free to use them. I also hope the state never gets one thin dime in taxes on them because the money will only be spent going on more murder sprees on the other side of the world in pursuit of empire building and enriching the most destructive and sociopathic people among us... Namely politicians, military leaders and others who make up the military industrial complex. We will never be a civilized nation until we stop pointing guns at everyone who does or says something someone else doesn't like.