Lashon, i never said chilul shabbos is not allowed for saving one’s life – it not only is allowed, it’s necessary and one who refuses to be mechalel shabbos for pikuach nefesh is considered a shofech damim.
However, al pi din we would not be mechalel shabbos normally for a person who does not keep shabbos, because the rationale of “break one shabbos so that he will keep many more” does not spply.
For goyim there’s literally no reason in the world to, but hatzolah does because if they don’t there will be hatred among goyim and they will not save us. This was a takanah of the vaad arba aratzos in the times of the shach.