A question in faith

According to the simple definition, there is no reason why it is forbidden because it is permitted and even obligatory. The law that it is forbidden was stated when the Gentiles did not behave humanely, as the Meiri wrote in the Yuma. Although the permission to violate Shabbat to save a life is based (for one reason) on the person violating one Shabbat so that he will keep many, according to this, even a secular person cannot be saved. Although the poskim wrote that the secular person can decide as he wishes, but I am obligated to give him the option to keep Shabbat, this is not very convincing. However, the Mairi wrote that it is not specifically about keeping Shabbats, but about any mitzvah (therefore, it is permissible to save even someone who lives a short life and does not keep many Shabbats). And this also applies to a gentile.