Cannabis should absolutely be legal. I get the impression that some people are not aware of the history of its prohibition. There were not always laws against possessing, eating, or smoking cannabis. It was a commonly used medicine throughout most of the world and it never caused a problem.
The push to ban cannabis on a global scale kicks off in the United States result of institutional racism and corrupt government bureaucracy. Racist law enforcement wanted an excuse to harass Mexicans in the U.S. and outlawing cannabis gave them that opportunity because its use had come to be associated with immigrant laborers. Saying that "we were looking for marijuana" became a convenient reason to stop and search Mexicans just for being Mexicans. At the same time, the prohibition of alcohol was coming to an end and there were a lot of federal law enforcement jobs that were about to go away. Instead of looking for new jobs, they chose this drug that was already being banned in areas for racist reasons and lobbied for it to be made federally illegal.
Once that had happened, the United States government started asking other countries to ban cannabis too and even made economic threats against countries that did not ban the drug. In time, the vast majority of countries outlawed cannabis and now we have the system that we know today.
In a sense, people who support keeping cannabis illegal are unknowingly doing the dirty work of the corrupt government officials, imperialists, and racists of the past. Though, I do not blame people for having been lied to. It is not their fault that they are misinformed about this plant, so, in my mind, they are not at fault.
There is more though. Cannabis has countless benefits for users and very few consequences. People may say that smoking is bad for one's health but that is not the only way to consume the drug. It can be cooked and added to a healthy food. It can be made into extracts or tinctures. There is even weed breath spray that will get you high and leave your mouth smelling fresh. These products are not just for having fun either (but having fun is still a valid reason for use). There are numerous health benefits. It can help people who have seizures, cancer, AIDS, and many other medical conditions that are both serious and trivial.
Cannabis is safe too. There are no deaths that can be reasonably attributed to the use of cannabis. Studies have shown that its smoke is less harmful than tobacco. The impairment that it causes has less of an impact on motor skills than alcohol which means its users are not as prone to accidents.
I could go on but this comment is getting pretty long.