Just do it.
These people have nothing to lose.
While you are at it, you might refer them to
http://www.magnesiumforlife.com/
This MD recommends Iodine, Magnesium and sodium bicarbonate (Baking Soda) for cancer.
Who cares if they think you are crazy?
If I were on my death bed and were offered an easy and cheap way to prevent it, I'd go for it.
After all, the MD's have failed them. This might make them more open to alternatives.
The reality is that they may not listen to you, I have this experience all the time, but I feel a sort of responsibility to try to help people. It's the good Samaritan thing. I think if you don't try, it will only harm you psychologically.
Throw them the life-saver, it's up to them to respond. You do your part though, for your own mental well being.
And may God bless this poor guy, he has my prayers.