Partially Wrong
What is partiality? In one sense, we are all partial - we have our own preferences and opinions. But James writes not of neutral preferences, but sinful distinctions. Such behavior stands in stark opposition to God's character, for He shows no partiality (Rom. 2:11), but discerns the heart. After his theological argument against partiality (that they were becoming judges with an unfair standard), James offers a pragmatic one: the rich they catered to were exploiting them! In the following verses, James will positively reference Abraham, who was extremely wealthy, indicating that the situation here is not rich versus poor per se, but rather ungodly rich oppressing the godly poor.
James deploys one final argument against partiality - it violates the law of love. God's law isn't a collection of independent commands but an interdependent whole, all serving the royal law: “You shall love your neighbor as yourself.” If we only think in terms of isolated edicts, we miss the forest for the trees, and can fail to see how far short we have fallen of the tallest commands to love God and love people. In V12-13, James shows us how to correctly see and live the law - through the lens of mercy. Paradoxically, the only way to obey the law is to first understand that we cannot. Through Jesus, mercy triumphs over judgment, showing us that loving our neighbor authentically stems from first experiencing the love of Christ.