I really don't think that this is something that can be compared to pedophilia or homosexuality... If you need to have a scripture that spells out that pedophilia is wrong, in order to understand that it is an abuse and sick.. then there must be thousands of other non-christian things that you would consider OK as well.
Sometimes it is obvious.
Now, with weed...
IMO and only my opinion... weed is no different than any other drug. Like alcohol, coffee, some teas have medicinal properties, aspirin, cloves, mint, the list goes on.
But, weed was illegal and the use of it is associated with those that are rebellious and of low character.
If my memory is correct, the original form of weed was hemp. Hemp was a very useful source of fiber for paper, rope, clothing and other products. But, it was a competition for pulp wood.
A very wealthy man owned a very large portion of land, very very large, that was to be used for pulp and paper. The biggest competition was hemp. Hemp was very low in THC and of very little value as a drug.
But, this man, with political clout, petitioned his minions in parliament to make the growing and selling of Hemp illegal. Even though it made better paper than pulp wood, needed less bleaching and the plant, itself, could be grown in poor soil and actually enriched the soil. Not only that but it produced more paper per hectare year in and year out than the much less environmental and less economically efficient pulp wood.
So, there you have it... and then.. as they say, tell someone that they cannot do something and what do they do.... go and do it... and... make a lot of money doing it..
Better plant strains and types were cultivated and produced... the rest is history..
This may not be the whole story.. but it is the short and sweet version.
So.. no.. it is not a sin to use cannabis where it is legal. But, the sinful things you do while under the influence........their still sins.
It is never good to use any chemical to the point that you lose your inhibitions.
We are always responsible for our actions.. Not to mention that our body is the temple of the Holy Spirit... we should treat it as it is a precious dwelling of this part of the trinity.
If Cannabis helps an ailment.... or medical condition.. or some other issue we have, and does not hurt anyone, put anyone in danger, put anyone in financial trouble... I see no reason for not being able to use it.. where it's legal.