In order to prevent another Jew from sinning are you allowed to steal the item he uses to sin with? For example assuming it is assur to smoke (Shu"t Tzitz Eliezer 17:21) can I steal another Jew's cigarettes to prevent him from smoking?
1) Rav Sternbuch in Tshuvos V'hanhagos chelek 1:368 answers a question very similar to this one. The questioner(a Bal Tshuvah) asks if he can damage his parents television.
The Rav answers that this is a machlokes between The Ketzos and the Nesivos in Choshen Mishpat siman 3(which discusses forcing someone to keep mitzvos).The Ketzos holds that the power of forcing someone to keep the mitzvos was only given to Beis din while the Nesivos holds it is on every individual. He writes that it seems even if one holds that it is on every individual still in order to take away someones money one needs a beis din ,and in many instances if one acts alone it can push the recipient even further away from mitzvos. He brings a gemara in berachos where someone acted in such a way and he brings the story with Rachel stealing the terafim which would imply that one can damage a sinful thing.
He ends off by saying that one should ask his Rav as every case is different,and the two proofs given the end of the story shows that maybe it shouldn't have been done.
2) The Be'er Moshe 1:60:10 towards the end writes about a case where a son should not get his father cigarettes if his father wants them or wants him to go buy. However , he writes:
אבל לילך ולהצניע" או לגנבו מאביו כרי שלא יהי׳ לו הסיגארעט להעלות עשן, בזה אני עדיין נבוך ולא ברירא לי ויותר נראה שלא יעשה כן"
"but to go and hid or steal from his father in order he doesn't smoke ,it is not clear to me but it seems that it is better not to."
3) Rav Nebontzol in his Kuntres Hanhagos writes if one is in a room with someone who has inappropriate pictures he can take them down without permission.
4) This is a very interesting case brought by Business halacha institute where a rebbi takes a mp5 player from student. http://www.businesshalacha.com/articles/educational-damage
There may be permission to do this, even to B'nai Noach (non-Jews). We see (Genesis 31:19) that Rachel stole her father's (Laban's) teraphim and hid them, with some commentators explaining that this was because she did not want her father to worship idols. (A Ben No'ach is prohibited from idol worship.) I would infer that if this can be done to a Ben Noach then it can be done to a Jew as well.