Rav Mordechai Rogov (a Mirrer) in his Ateres Mordechai talks about the strange juxtaposition in the criticism of Amon and Moav- that they didn't come out to greet you with bread and water, and that they hired Bilaam to curse you, in the hope that you would all die. This is like saying that they lack refinement, and they are monsters. Some answer by saying that if they would defend themselves by saying that they were poor, and they couldn't afford to give you anything, and they were afraid you would descend upon them and impoverish them, then how did they manage to find the enormous amounts of money they offered Bilaam to curse you?
Harav Rogov simply answers that the foundation of murder is indifference.
This reminds me of something written by Agamben. Harav Rogow doesn't need support from Agamben, but Rav Rogow was famously brief and expressed his deep thoughts with disarming simplicity, so it's interesting to see the idea elaborated in modern language. I took the following from Wikipedia. The basic idea is that the first and essential step taken by a society before countenancing or even encouraging murder is removing the victim’s identity as an equal, as a citizen, and someone like yourself.
Homo sacer (Latin for "the sacred man") is an obscure figure of Roman law: a person who is banned, may be killed by anybody, but may not be sacrificed in a religious ritual. The person is excluded from all civil rights, while his/her life is deemed "holy" in a negative sense.
Italian philosopher Giorgio Agamben used this concept for his book Homo Sacer: Sovereign Power and Bare Life. Agamben describes the homo sacer as an individual who exists in the law as an exile. There is, he thinks, a paradox: It is only because of the law that society can recognize the individual as homo sacer, and so the law that mandates the exclusion is also what gives the individual an identity.
Agamben holds that life exists in two capacities. One is natural biological life (Greek: Zoë) and the other is political life (Greek: bios). This zoeis related by Agamben himself to Hannah Arendt's description of the refugee's "naked life" in The Origins of Totalitarianism (1951). The effect of homo sacer is, he says, a schism of one's biological and political lives. As "bare life", the homo sacer finds himself submitted to the sovereign's state of exception, and, though he has biological life, it has no political significance.
Agamben says that the states of homo sacer, political refugees, those persecuted in the Holocaust, and the "enemy combatants" imprisoned in Guantanamo Bay and other sites are similar. As support for this, he mentions that the Jews were stripped of their citizenship before they were placed in concentration camps.
Thus, Agamben argues, "the so-called sacred and inalienable rights of man prove to be completely unprotected at the very moment it is no longer possible to characterize them as rights of the citizens of a state", following in this Hannah Arendt's reasoning concerning the 1789 Declaration of the Rights of Man and of the Citizen, which tied human rights to civil rights. Although human rights were conceived of as the ground for civil rights, the privation of those civil rights (as, for example, in the case of stateless people or refugees) made them comparable to "savages", many of whom were exterminated, as Arendt showed, during the New Imperialism period. Arendt's thought is that respect of human rights depends on the guarantee of civil rights, and not the other way around, as argued by the liberal natural rights philosophers.
Elie Wiesel said this in a powerful way. He was quoted in the US News & World Report (27 October 1986) as having said
The opposite of love is not hate, it's indifference. The opposite of beauty is not ugliness, it's indifference. The opposite of faith is not heresy, it's indifference. And the opposite of life is not death, but indifference between life and death.
Update Ellul ayin vov/September 2016
I saw that Reb Yaakov (a Slabodker) here in 21:23, in his Emes L'Yaakov, talks about the Torah's apparent double warning not to leave an executed criminal's body hanging- לא תלין נבלתו על העץ וגו' ולא תטמא את אדמתך. He shows that the words ולא תטמא את אדמתך are another way of saying that leaving the body hanging will result in more murders committed. Why? Because the natural sense that human beings have a divine element, and have infinite value, will be depreciated upon seeing the disgraced body- not only the disgraced body, but the fact that it was disgraced by other people. So here, too, in sequential parshios in Ki Seitzei, we see that you don't prevent homicide by telling people that (as Reb Yomtov Ehrlich puts it!) killing people is not nice. You have to start far, far before that- you have to teach people to be respectful and to see the divine in their fellow human beings.
כ"א כ"ג לא תלין נבלתו על העץ וגו' כי קללת אלקים תלוי ולא תטמא את אדמתך פירש"י וז"ל כי קללת אלקים תלוי זלזולו של מלך שאדם עשוי בדמות דיוקנו כו' כל הרואה אותו אומר המלך הוא תלוי וכו'
והנה עיין ברמב"ן שהעלה דטעם דולא תטמא את אדמתך הוא לאו מיוחד לארץ ישראל והיינו דהמלין את התלוי עובר בארץ ישראל בלאו נוסף של טומאת הארץ והרי הוא עובר בשני לאוין ועשה ובחוץ לארץ כלאו ועשה ועיי"ש
ולפענ"ד ביאור הענין הוא עפ"י דברי רש"י הנ"ל דהתליה הוא ביזוי לצלם אלקים דהרי כשמתבזה צלם אלקים זה גורם לשפיכות דמים וכמש"כ בפרשת נח ט' פ"ה ואך את דמכם לנפשתיכם אדרש גו' כי בצלם אלקים עשה את האדם והיינו שהאזהרה לשפיכות דמים היא משום שהאדם עשוי בצלם אלקים וא"כ כשמבזה את הצלם הרי הוא מרבה שפיכות דמים ושפיכות דמים גורם לטומאת הארץ וכדכתיב לעיל בפרשת מסעי ל"ה פל"ג ולארץ לא יכפר לדם אשר שפך בה כי אם בדם שפכו ולא תטמא את הארץ אשר אתם ישבים בה וגו' וכן איתא ביומא דף פ"ה ע"א ושפיכות דמים מטמא את הארץ וגורם לשכינה שתסתלק מישראל והביא רש"י פסוק דה בפרשת מסעי ולכן כארץ ישראל ישנו טעם נוסף של ולא תטמא את אדמתך דהבזיון לצלם אלקים כהכרח יגרום הוספה בטומאת הארץ ודו"ק היטב
In light of these two observations about homicide, and the Rashi about Ben Soreir uMoreh, the Parsha is teaching us the aleph beis of Mussar: Seemingly minor ethical debasement, left unaddressed, can lead to the most brutal and bestial behavior. A pegam in middos can lead to the worst aveiros if left uncorrected.
(The Rashi in 21:11-
[and you desire her,] you may take [her] for yourself as a wife: [Not that you are commanded to take this woman as a wife,] but Scripture [in permitting this marriage] is speaking only against the evil inclination [, which drives him to desire her]. For if the Holy One, blessed is He, would not permit her to him, he would take her illicitly. [The Torah teaches us, however, that] if he marries her, he will ultimately come to despise her, as it says after this, “If a man has [two wives-one beloved and the other despised]” (verse 15); [moreover] he will ultimately father through her a wayward and rebellious son (see verse 18). For this reason, these passages are juxtaposed. — [Tanchuma 1] )
(The Rashi in 21:11-
וְרָאִיתָ בַּשִּׁבְיָה אֵשֶׁת יְפַת תֹּאַר וְחָשַׁקְתָּ בָהּ וְלָקַחְתָּ לְךָ לְאִשָּׁה:and you see among the captives a beautiful woman and you desire her, you may take [her] for yourself as a wife.
ולקחת לך לאשה: לא דברה תורה אלא כנגד יצר הרע. שאם אין הקב"ה מתירה ישאנה באיסור. אבל אם נשאה, סופו להיות שונאה, שנאמר אחריו (פסוק טו) כי תהיין לאיש וגו' וסופו להוליד ממנה בן סורר ומורה, לכך נסמכו פרשיות הללו: