In The Arabian Knights, brothers (and sultans) are victims of adulterous wives...and both kill them. Then they marry a new wife each day and have her executed in the morning, after spending the night with her. One is Schahriar or Shahryār; the other is Shahzaman.
Now the Sultan Schahriar had a wife whom he loved more than all the world...It was therefore with the deepest shame and sorrow that he accidentally discovered...that she had deceived him completely, and her whole conduct turned out to have been so bad, that he felt himself obliged to carry out the law of the land...to put her to death.
It is on this premise that the story is structured: Scheherazade comes up with a plan to be the Sultan's next wife, hoping to put a end to this practice. With the help of her sister, Dunyazad (who asks her sister to tell a story), Scheherazade plans her evening, telling one story and starting another—only to run out of time. The "cliff-hanger" that is unfinished so intrigues the Sultan that he spares her life another night, and the stories continue until he falls in love with Scheherazade.
Should the husbands be appalled? In most cultures, the answer is "yes." Schahriar carries out the punishment according to "the law of the land."
The story's setting tells us a great deal about the "law of the land." It is...
...a collection of Middle Eastern and South Asian stories and folk tales compiled in Arabic during the Islamic Golden Age.
Brilliant men of the Islamic nation of the Islamic Golden Age were influential in changing the entire world. Areas to which they contributed were...
...agriculture, the arts, economics, industry, law, literature, navigation, philosophy, sciences, sociology, and technology.
The culture was forward-thinking in many ways: open to individualism, freedom of speech, and religious freedom. This information shows that this era was not a time of backward thinking or uncivilized behavior.
However, Islamic law was long-standing and not to be taken lightly. Adultery was (and is) punishable by death (by stoning—called "rajm"). With this in mind, the standard of behavior expected by one's wife in the culture if Islam is fidelity (faithfulness). The severity of the punishment infers the importance of this law.
The displeasure of adultery in the U.S. is based upon ethics and religion; with the separation of church and state, adultery may only become "punishable" within the court system when divorce is involved—and punishment is seen with division of property, custody disputes regarding children, etc. There is the same stigma with regard to adultery: it is considered wrong by many, but the consequences in the U.S. are much different than in an Islamic culture.
The husbands in One Thousand and One Nights (or The Arabian Nights), based on cultural mores, did have the right to be appalled by the behavior of their wives under Islamic law.