There is a big difference between a sin and a crime. While as a Christian I do not believe getting high is a crime (that falls under "Caesar's law" kind of thing), I DO believe it is a sin (since any abuse of the body, or anything that takes us farther away from God, is a sin).
It's not a crime to be angry over petty things, but it is a sin.
It's not a crime to go into debt, but it is a sin.
It is not a crime to be addicted and to have other moral failings, but that does not make them not sins.
Legalizing marijuana is fine, because marijuana is an herb designed with a specific purpose to help people, and if it's abused than those people need help and encouragement in overcoming their addiction without fear of being put in jail. Abusing it, however, is spiritually damaging.
There is a proper way to overcome sadness, ways that strengthen the spirit and our relationship with God. There are lots of good, wholesome ways to have fun that do not damage our relationship with God.
That makes me sad, seeing a poll like that.
"Moderation in temper is always a virtue; but moderation in principle is always a vice." -- Thomas Paine