My point is, who are you to decide what is "lousy and destructive behavior" for everyone? Marijuana is clearly not for you.

For some however, it is a very real solution to problems like anxiety, insomnia, depression, low appetite, etc. Marijuana often has fewer side-effects than medications prescribed for those same ailments, making it a better option for many. That is how some people justify consuming the drug, and I think it's pretty narrow-minded to assume anyone who makes such a justification is an addict.