In the airline industry elevation = height above ground and altitude = height above sea level. Altitude is used to calculate air pressure, elevation is used to make sure you don't crash into mountains.
Marijuana is a dangerous and addictive drug that has many consequences to using it. People debate whether it should be legalized or not due to its pros and cons. Marijuana should not be legalized because it is a gateway drug to the legalization of other drugs and has many bad effects on the users of it.
We really shouldn't have to ask why marijuana should be legal; the burden is on the government to show why it shouldn't, and none of the explanations for marijuana prohibition are especially convincing. But as long as we have to deal with the reality of marijuana laws, we can present a strong case for repeal.