What does this quote from Things Fall Apart mean? "The world has no end, and what is good among one people is an abomination with others."

This quote is highly significant in light of the major themes of Things Fall Apart. The second section of the novel is especially concerned with differences in cultural outlooks and discrepancies of moral perspectives.

Pointed conflicts emerge -- and become central to the novel -- as a result of the differing value systems of the Igbo people and the British people. The Christians who arrive to colonize the region adhere to a set of beliefs that in many instances run counter to the beliefs of Umuofia and the surrounding villages. Where Igbo beliefs sanction the scarring of stillborn babies to ward off stillbirths in the future, the English Christians see this act as "an abomination." 

When the English begin to mix and mingle with outcasts, the Igbo feel that line is being crossed. The British are engaging in taboo actions. Thus, the perceptions of each group is depicted as arising from differing cultural backgrounds that do not easily translate. The legal, social and religious systems of the Igbo people are intertwined as are those of the English Christians, seemingly amplifying the difficulty of a cross-cultural understanding. 

What is acceptable for one culture is unacceptable for another. 

The quotation in question relates to the novel's repeated concerns with localized and historically-determined customs and is echoed at the end of Chapter Eight in a conversation between Okonknwo, Obierka's and Obeirika's family.

Here, the men discuss other Igbo villages where "titled men climb trees and pound foo-foo for their wives." 

"All their customs are upside-down. They do not decide the bride-price as we do, with sticks. They haggle and bargain as if they were buying a goat or a cow in the market."

"That is very bad," said Obierika's eldest brother. "But what is good in one place is bad in another place."

The notion expressed in this quotation is the same as first quotation discussed. Ideas of proper action (morality, ethics, and etiquette) are distinct from place to place, even when those places exist within a very similar cultural milieu and share overlapping histories. 

In exploring differences in moral perspectives and worldviews, Achebe's novel suggests that (1) people do indeed understand that customs are relative and derive from cultural histories but (2) the understanding of this fact does not necessarily lead to the development of cross-cultural empathy or sensitivity. Each culture may continue to insist on enacting the codes and customs of its own social history even if that means undoing, contradicting or ultimately destroying the codes and customs of another culture.

The nature of the British occupation is problematized by the novel's explicit awareness of the ways that cultural norms are valid (only) within a specific context and should not (or cannot) be justifiably universalized.