Signatories include names you might recognise, like Ron Sider, Lewis Smedes, Jim Wallis. Though if you have not been following the general movement that considers itself focused on social justice the last fifty years, even those names may not mean much to you.
I should let it speak for itself, but I will give you the hint that it connects very strongly to my recent link to CS Lewis's The Dangers of National Repentance. In the 1973 Chicago Declaration of Evangelical Social Concern, they spend their time confessing other people's sins. It's pretty clear they don't mean themselves. They are decent enough people, and usually have lived exemplary Christian lives. But they don't see what they are saying here. (Sider did later admit that he didn't know much economics when he wrote Rich Christians in and Age of Hunger.)
Contrast this to the courage of the Barmen Declaration as Nazi Germany was getting under weigh.