Say that Reuven smokes. Shimon knows that smoking causes lung cancer, and has tried everything he can think of to help Reuven stop. For that matter, he's gotten the other ten Shevatim, the Avos, and anyone else you can think of in Tanach, Tzaddik or Rasha, to try to talk to Reuven and get him to snap out of it to no avail.

What, you don't like my sense of humor?

Though I suppose I lied. There was one other thing he could thing of: he could always just steal the cigarettes and dispose of them in the nearest dumpster so that the rats get lung cancer instead. (This question has nothing to do with tza'ar ba'alei chaim, don't worry.)

Is he allowed to do so? The Gemara in Bava Metzi'a (61a) says it's assur to steal from someone even if it's for their benefit. Would that apply here?

There's also a question about lo sa'amod (ta'amod for you Sefardim out there) al dam reiecha. I would assume one is allowed to damage others' property in order to save a life. Would this fall under that rubric? Is preventing a long-term deadly disease considered part of lo sa'amod?

Is there a lifnei iveir issue that he'll hate you for stealing (possibly repeatedly) from him? Does it matter in the face of saving his life?

Are there any other issues that I haven't thought of?

(Let's assume that smoking is not an aveirah, as, if it is, this question already deals with the issue.)