Bkvod Harav
Shavua Tov
In the other cases of Nitan l'Hatzilo b'Nafsho, the person stopping the person from doing an aveira is himself not violating an averia, with the exception of the killing, which is deemed not an averia.
However, in the case of ha'Mechalel Shabboa Nitan l'Hatzilo b'Nafsho , if one were to kill the one about to commit the Chilul Shabbos, would himself also be oiver on Chilul Shabbos since this can only take place on Shabbos?
Why would we think that one person having to be oiver on Chilul Shabbos and killing an other to prevent his Chilul Shabbos is better than not preventing someone else from being oiver on Chilul Shabbos but himself not being oiver on Chilul Shabbos?
Kol Tuv
Besuros Tovos
Interesting question! Three possible answers:
1)It is learned out from a Gezeira Shava, and as such even if logically it is not understood this is the decree of the Torah.
2) Just like one may save another Jew's life with Chilul Shabbos, so too one may break Shabbos to save him from such a terrible Aveiro
3) Killing a person to stop him from doing an Aveiro is not Chilul Shabbos. It is a Melacho She'eina Tzricha l'Goofa, which according to Rov Poskim is only Assur Derabonan. Even according to the Rambam that it is an Issur D'Oraiso, seeing that one doesn't want the death of the transgressor (only to stop his Chilul Shabbos), it is a Mis'aseik (different from, but) reminiscent of catching a snake so it shouldn't bite you which the Rambam permits. (I'm not sure that what I wrote about the Rambam is true but I offer it as legitimate food for thought).
Shimon Brodie