Ki Seitzei, Devarim 23:4. They Were Not as Kind as they Should have been to You. Also, They Hired Someone to Have You All Killed.

Rav Mordechai Rogov in his Ateres Mordechai talks about the strange juxtaposition of the complaint against Amon and Moav- that they didn't come out to greet you with bread and water, and that they hired Bilaam to curse you so that you should 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 zoe is 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.

To me, the most interesting thing about this is the insight we gain into “ve’ohavto le’rei’acho komocho.”  Komocho is not a shiur, it’s essential to the idea of respect of another human being.  If you take away the komocho, you might come to stripping him of his identity as a fellow human being, you might eventually be indifferent to his right to life.  Amon and Moav didn’t see you as human; if they had, they would have offered you something to eat and drink.  Once they ‘otherified’ you, it was an easy step to cursing and attacking you.