Yes, that's Paul's argument. We know that. Everyone knows that.
The point we are discussing here is James is NOT contradicting Paul by saying a man must be justified by works. His justification by works does not mean the same thing as Paul's justification by works. That's what the church does not get. And so they are sure they do not have to have works to be saved when Jesus comes back.
We have people reading this that need to understand. And you are right, "the church" ....a lot of people do not understand. Christianity has in a lot of ways, has become a "don't doers" religion because of the mix up between works of the Law and good deeds. A lot Christians understand "righteousness" as what you don't do...the sins that you don't do. But what you are saying can confuse people. Justification is linked to the Grace of Christ. After we believe and are saved...we cannot do "a do" that has anything to do with salvation.
But we can do things that can send us to Hell, that is why the Apostles spent so much time warning Christians about sin and listed the sins that can send Christians to Hell. Good deeds are a reflection of Christ in us. How can we say we understand Christ when He said to love one another, if we do not help one another.....it is a very important point but it can be confusing by how you are wording it. Christians can go to Hell because of their sins, the Apostles kept warning about that.
Christ made it clear that if you do not love one another, if you do not have compassion for one another, and if you do not help one another, you do not know Him and He does not know you. That is what sends you to Hell and that is how Christ worded it...He does not know you. James used the word justification and that is unfortunate. We cannot be good enough to be saved by our own actions. But obedience is required. Why do you call me Lord Lord and not do what I say.... You cannot call Him Lord, if you do not do what He says. And He says to love one another. Be good and do good the best you can....and that is all He is asking.
Christianity is not a club you sign up for and go on about your business doing what you want. As a followers of Christ we obey what He says. If we were not sincere...He knows that...and we were not saved to begin with...we cannot play Christ for a fool...He knows our heart. We cannot claim Grace if we were not sincere and that is the contingency for forgiveness. If we had the faith of a mustard seed we could move mountains....but as humans our strength of faith is at the human level and that is all that Christ asks. But faith means a commitment, an honest intent. So the point is good deeds are not an option. If you truly know Christ, you will do good deeds.