Firstly marijuana is not physically addictive. This means the body will not crave the way it will with other drugs such as heroin where people become so addicted that they have to take the drug or they will get very sick or may even die. This means it will be easier to come off the drug because their body will not depend on it.
That brings me to my next point. Marijuana is a weak drug compared to other such as P, Heroin, Cocaine and ecstasy. These dugs overdosed on can put a person in the intensive care unit or even kill them. There are hallucinogens like magic mushrooms and LSD which will make you do things to yourself like cut yourself or commit suicide.
Marijuana can be taken as a pain reliever. For example people who are in pain may not be able to take other pain relief drugs so have to take marijuana. The chemical in marijuana that gives pain relief is also found naturally in the body. So marijuana is just amplifying what occurs naturally anyway.
Marijuana has one of the smallest death rates in the world compared to other legal drugs such as alcohol and tobacco. Alcohol itself is one of the biggest causes of death in the world.
Although marijuana is not as bad as other drugs it can lead you onto those harder drugs such as cocaine, heroin, ecstasy and P. So if we legalize marijuana people after awhile are going to get board with it and move onto these harder more dangerous drugs.
While marijuana does not affect the body like these other harder drugs it can still do some really bad things to you like make you confused, panic, have psychotic episodes, ruin your co-ordination and all other sorts...