Spanking: How Does the "Rod" Translate?

While reading the psych textbook, I came across and interesting tidbit of information. On page 216, it says that

Spanking alone is already a controversial issue. Most of us agree that dicipline should lie somewhere between breaking a child's will, and providing no guidance for behavrior.

However, when looking at the ways that culture plays a role, things seem to turn so much more "gray". Why is it postive in some cultures and negative in some? Why is it correlated with aggression in some places but not others?
Personally, I think there may be a role in how children view what is "normal". Children may associate their parent's love with how other parents treat their children.

What do you guys think are some of the reasons that culture affects children's behavior so strongly? Being from another country, I am especially interested in seeing how race and culture alters our perceptions as people.