But you have insulted the poor.(Now, before I continue on with this discussion, I think that it might be important to do a little background here. Consider the commentary on James 2:2-4, and also consider James 1:9, 10, & 11.)
Is it not the rich who are exploiting you?
Are they not the ones who are dragging you into court?
Are they not the ones who are slandering the noble name of him to whom you belong?
These two verses are very real-word-ish or maybe you could describe them as a reality check. It is almost like James is saying, "...umm guys. Ignoring the wrongness of discrimination based on the outward for just a moment... You are insulting the poor people, when it is the rich people who are doing all of this stuff. Your logic doesn't even make sense!"
Sometimes it can be very useful to take a step back and really look at things. Really look at the results of our actions or really look at the logic of our reasoning. God's word is true, but guess what... God's word is really true. It is true in this world that we live in, not just in some hypothetical universe.
Outward appearances do not always show a reality. Riches do not always mean the blessing of God and being poor is not a curse.