"An Amonite or a Moabite shall not enter the congregation of Hashem ..., to eternity, because they did not greet you with bread and water on the road when you were leaving Egypt, and because he hired against you Bilaam son of Beor ..." (Devarim 23:4-5).

A convert from Amon or Moav may not marry into the Jewish nation, even after many generations.  This appears a severe punishment for such a seemingly minor infraction.  The Egyptians enslaved, tortured, and killed us and yet they may marry into the Jewish nation after three generations.  Amon and Moav, on the other hand, did not physically harm us.  Furthermore, the latter portion "because he hired against you Bilaam son of Beor" only applies to Moav, why is Amon punished as severely as Moav?

Rashi's approach (based on Sifri) is that there is a deeper hidden meaning behind what is written explicitly in the text.  The Torah is referring to Bilaam's plot to compromise the purity of Bnei Yisrael. (Kli Yakar discusses the interface of pshat and drash, and how Rashi would understand Amoni  v'lo Amonit, but that is beyond the scope of this piece)

Ramban points out that Amon and Moav, descendants of Lot were recipients of the kindness of Avraham who risked his life to save Lot from captivity.  It was in Avraham's merit that Lot and his daughters were saved from Sodom.  Basic human gratitude would have them, at a minimum, to greet the children of Avraham with bread and water.  This is a glaring lack of Hakarat HaTov, returning disfavor in place of favor, rendering evil for good.

Sefer HaChinuch emphasizes the importance of gemillut chesed and the repulsion of utter rudeness.  The Moabites public disdain of civil behavior highlights the degree of their baseness.  There was no longer chance for them to correct their behavior.  Depravity so entrenched cannot be made right.

Our Halachic tradition limits the prohibition to males.  The daughters of Amon and Moav are permitted to marry into the Jewish nation.  They were not expected to go out and greet wayfarers and cannot be accused of improper middot (character attributes).

Sefer HaChinuch describes Amon as 'naval' - churlish (boorish).  Interestingly, there was a person named Naval in Tanach, who was certainly not a positive character.  He refused to feed David HaMelech and his army, even though they had protected Naval's shepherd and flock.  David declared that Naval had rendered evil for good.

Avigail, Naval's wife was kind, intelligent, and gracious. She prevented bloodshed, and eventually married King David.  Apparently there is a pattern of churlish males and kind females, as we find with Amon and Moav, Avigail, and of course Ruth who descends from Moav.

A brief look at some of the Mitzvot in the parsha will give us an inkling of the attitude we should have toward others. We must return lost objects, help with loading and unloading, refrain from taking interest, pay laborers promptly, trade fairly, judge honestly, refrain from entering a debtors home to take a bond, leave corners of the field for the poor,  be dedicated to one's wife, and keep our word.

Too often we see ostensibly religious people acting horrendously. We've heard appalling speech, and seen terrible behavior. During the month of Elul perhaps we can improve our thoughts and actions. Care for others and do for them what we would expect a proper Jew to do for us.