RebDoniel, much of the sefer can be read for free on Google Books.
Whiteberry, let’s forget about Hillel for a second. What about Rabbi Akiva? If we truly believe that the root of the Torah is, what is hateful to you, don’t do to others, then isn’t it obvious why we shouldn’t harm any non-Jew? Because if we always put ourselves in others’ shoes and empathize with them, we will treat all of G-d’s creatures with respect and compassion, thus emulating Hashem’s traits, just as Chazal repeatedly emplore us to do.
Farrocks, I’m aware of that interpretation. There are others. See Sefer HaBris. Whether it’s meant as halacha or homiletics, it’s worth reading.
A nice quote from Ramak’s Tomer Devorah: One “should be a father to all the creatures of the Holy One, Blessed is He, and to
Israel in particular… And he should constantly pray for mercy and blessing for the world just as the Supernal Father has mercy on all His creatures. And he should constantly pray for the alleviation of suffering as if those who suffer were actually his children and as if he had created them.” Of course, we have a special love for fellow Jews, but that does not mean we should not be compassionate toward non-Jews as well.