Wang Lung is disgusted with his uncle's crooked ways, but has no choice to lend him money because of his familial obligation to him. In traditional Chinese culture, respecting your older family members and constantly helping them out is highly valued, whether they deserve it or not. If he doesn't help his uncle out, he will be looked down upon in his society and ridiculed for it. They will judge him poorly for it. If he wants to remain in good standing in his community, he has no choice but to continue to be exploited by his uncle.