If you want to smoke pot, that is fine with me. However, being on a ship where someone in a cabin VERY near mine decided to indulge in their vice, I was upset when it did affect me and my vacation. I smelled the damn weed anywhere in the corridor and inside my cabin....and I did NOT pay for that added feature. So, I don't think that allowing it on cruise ships is a good thing.....way to many people in a very enclose space can be subected to your smoke.
And, yes I do think marijuana does have some medicinal uses, with regards to nausea. But unless you are in your own home, where does the line get drawn? If in an acute care or long term care facility, how can you justify the odor spreading to other areas? Don't other people have rights to NOT be affected by your use? It is a sticky wicket as my english friends would say.