The Torah mentions two reasons for not accepting the Amoni and Moavi into Klal Yisrael. The first appears to be a character flaw; the second seems more substansive. We can understand taking a strict attitude towards a people that have sought to harm us, but why should their lack of decency play a role in their rejection as converts? Chazal give a number of reasons for this. Horav Nissan Alpert, zl, offers a thoughtful insight into their behavior which demonstrates their utter hatred for the Jews. Consequently, he explains why such a people should be eternally excluded from joining Klal Yisrael.
The criticism against Amon and Moav is not based upon their lack of character, but rather upon their baseless hatred of the Jewish People. It would make sense that as a result of the terrible destruction that Hashem wrought against the Egyptian people, every surrounding nation would have developed respect for the Jews. Indeed, we assert in the “Shirah” that all the nations trembled with fear of Klal Yisrael. When Klal Yisrael passes by, what would be the intelligent response? Welcome them with food and pay your respects to them. Surely, do not incite them. Amon and Moav’s hatred for the Jews was so intense that they were willing to die like the Egyptians, if necessary, in order to have no interaction with the Jews. Such unwarranted hatred is intolerable. Such people have no right to enter the fold and to be accepted as Jews.
Yet, there is one mitigating factor that we should address. At least Amon and Moav are people of principle. As true antisemites, they feel their hatred is too overwhelming to even effect a pretense of acting as decent human beings to a nation that is homeless, who has endured hundreds of years of slavery and deprivation. Perhaps, if they were to be accepted into Klal Yisrael, whatever hatred had been manifest towards us would dissipate.
For this reason, the Torah includes the second reason–the hiring of Bilaam. If Moav had been such a principled people, how could they permit themselves to hire Bilaam — their arch enemy from Midyan –even before the Jews came upon the scene? In fact, they did not simply hire him, they responded to him as long lost friends! This demonstrated that their code of principles is as worthless as they are. When it is for their benefit, their principles suddenly disappear. As a result of their unusual hatred, they did not even greet the Jews. We have no place in our nation for such miscreants.