Don't get me wrong social justice is integral to the gospel. James makes it perfectly clear that you cannot be a true believer if your belief is not back by deeds to those in need (James 2:14ff). The problem comes when people become convinced that if they do good works then they are a christian. The reality is that if you are a true believer you should find yourself compelled to do justice because of the renewing power of the Holy Spirit in your life.
Now we know that this doesn't happen. So why doesn't it happen? Well basically for the same reason that James had to write his epistle; people are confused through the deceiving power of the world and need to have the situation clarified.
This confusion is basically the converse of the Social Gospel and equally misguided. I have even heard the story of Peter healing the lame beggar (Act 3:6) used as a justification that we should concentrate on "winning soles" not on social justice. But the whole point of the passage is to show that the two are inseparable. You cannot have one without the other and call it Gods Good News (Gospel).
The history of the church is profoundly full of Social Justice busting out whenever there is a world wide revival. This is seen no more clearly than the establishment of the the Salvation Army. Where their Slogan of "Heart to God hand to man", is the most theologically sound and succinct expression of what the true motivation of Christians should be. How could you not be inspired by the call to fight no matter what denomination you belong to.
When we look at the state of the church generally, in western society we are loosing the spiritual war at the moment. I don't believe that God will allow that to continue indefinitely; it will turn about. But for the moment, we are focusing on the wrong thing and we need to turn that about.
As Christian we will always have to struggle with political agendas and we will always have a drive to win soles but we must always struggle to make neither of those our main focus. Our main focus should always be people.
Maybe this video will help you understand what I'm talking about.