The apostle James begins chapter 2 of his epistle by confronting a problem that frequently rears its head in the church, that of respect of persons, also called partiality and discrimination. His entire thought in introducing the subject runs as follows:
My brethren, do not hold the faith of our Lord Jesus Christ, the Lord of glory, with partiality. For if there should come into your assembly a man with gold rings, in fine apparel, and there should also come in a poor man in filthy clothes, and you pay attention to the one wearing the fine clothes and say to him, "You sit here in a good place," and say to the poor man, "You stand there," or, "Sit here at my footstool," have you not shown partiality among yourselves, and become judges with evil thoughts? (James 2:1-4)
The example he gives is a common one. Human nature tends to be partial to the rich, the well-groomed, the finely appareled—those who make a good outward show of respectability. It is rather selfish of us to pay them so much attention and provide them with favors and upgrades that we would not normally lavish on others. We do these things because we want something from them, whether it be some future benefit we might receive as gratitude for our obsequious solicitation or merely to be seen with them, ratcheting up our status as a result. Respect of persons is, at its base, all about us.
Of course, it also diminishes those we pass over, essentially telling them, "You are not worthy of my time or favor. Take care of yourself . . . over there . . . where you'll be out of the way." Such partiality actually turns the godly order on its head. Those who are wealthy or powerful or good-looking or talented need no help; they are successful and prove by their success that they can take care of themselves. The poor and downtrodden, however, are the ones who need our help to give them a hand as they start up the ladder of recovery and eventual success. Human nature perversely offers help and advantage to those who need it least and denies it to those who desperately seek it.
Even so, James' central thrust in this long paragraph (which stretches all the way to verse 13) is that favoritism is wrongful judgment: "have you not . . . become judges with evil thoughts?" His argument against partiality obviously derives from his half-brother's comments on judging in Matthew 7:1, "Judge not, that you be not judged," where Jesus goes on to speak about a person's method of judgment of others being used by God to judge him. Jesus calls the one who judges his brother a hypocrite because he condemns his brother for a minor fault (a "speck") while he himself has much a larger sin (a "beam") to overcome. Thus, practicing partiality makes us judge, jury, and executioner of a fellow Christian—not to mention that we poach on one of God's prerogatives, sitting on His throne as judge.
James is speaking about unjustified discrimination. The distinction made between the rich man and the poor man in his example had its basis in purely outward and superficial reasons, and thus the judgment was unsound—or as he puts it, "evil." As the apostle points out in verse 5, God more often calls the weak of the world to righteousness (see I Corinthians 1:26-29), so the poor man is just as likely—or perhaps even more likely—to be the more converted of the two. This is not always the case, but it does make James' point that we need to be more thorough in our discernment of people lest we judge them by sight rather than by faith (II Corinthians 5:7).
Our example of this is God Himself. When the prophet Samuel went to Bethlehem to anoint the next king of Israel, he saw the strapping older sons of Jesse, thinking, "Surely it must be one of these!" But God saw things differently: "Do not look at his appearance or at his physical stature, because I have refused him. For the LORD does not see as man sees; for man looks at the outward appearance, but the LORD looks at the heart" (I Samuel 16:7). The "poorest" of the family was chosen, as David was the youngest and smallest, the one that everyone seems to have forgotten about to the point that no one had thought to tell him that Samuel was in town!
Being quite limited in our spiritual perception, we have a hard time doing that, so our best course is to treat everyone with humility and kindness, preferring them in our interactions with them.