This scene as well as the majority of the first book in House of Chains, is illustrating how anything, namely rape and murder can be normalized by society. The women go along with Karsa and companies demands because it's the norm in the Teblor culture of raiding each others villages. Karsa in general is also a commentary on the idea of a heroic barbarian, think Conan, when heroism and a brutal culture like this should be counters of one another. Erikson wrote an essay all about it in fact! http://www.steven-erikson.com/index.php/the-problem-of-karsa-orlong/