Also, every marriage is different in Ibo society, just like in any other. Some of the men have very close relationships with their first wives, even though they marry other women. Okonkwo however sees this as weakness, and establishes the same discipline with his entire family.
Although spousal abuse is not usually a crime in Ibo society, it can become one due to circumstance. For example, when Okonkwo beats his wife during the Week of Peace, he must pay a fine of atonement to the gods. In addition, the trial in Chapter 8 centers around a woman who has left her husband because he beats her regularly and excessively. He takes her family to court to essentially sue & gain her back. The egwugwu find in her favor however, saying she had the right to leave him because of his violence.
As for the polygamy aspect, I'd like to add that the family dynamics are presented in a fairly positive light...at least as far as the wives/children are considered. There doesn't seem to be jealousy among the wives, and their children grow up quite close, seeing each wife as a mother.
Unfortunately, wives (and women in general) are not always treated favorably in Ibo society. However, polygamy is a well-established and even respected practice within the culture.
Unlike the initial reactions of many in the western world, the idea of polygamy does not conjure up fantasies of Dionysian excess for those within this culture. In fact, having many wives was not only a sign of social standing but also one of responsibility and duty within the society. It was only men who could financially support but also lead and manage multiple households who engaged in the practice.
Polygamy is an absolutely acceptable thing in Igbo culture. The men who are able to provide for multiple women and their families are considered great men and worthy of great respect. An example of this is of course Okonkwo and his multiple wives and his constant desire for more. This has more to do with the search for respect and power rather than a desire just to sleep with more women, etc. His incredible work ethic drives him to try and support his families and wives as best he can.
Of course, the darker side of Okonkwo is that he also beats his wives and is incredibly short tempered with them. This is somewhat accepted as a part of culture, but there are also consequences brought about by the community because of his constant violence and inability to control his temper. It is as though there is a level of acceptable violence or abuse but if you go too far, there are consequences.