It isn't the social activism that makes a church squishy. It's that the social gospel is not the Gospel:
Surely there is much in the tradition for which to be grateful. Yet even a brisk reading of Rauschenbusch's work suggests crippling weaknesses, at least from the standpoint of faith. We're told that the larger social message of Jesus' teaching--especially his concern for the poor--was sidelined by the cultural assumptions of his followers. The culprits: the doctrine of sin and the "crude and misleading" idea of a coming apocalypse. Generations of believers wrongly came to regard earthly life as a snare and turned inward for personal salvation. "Such a conception of present life and future destiny," Rauschenbusch wrote chidingly, "offered no motive for an ennobling transformation of the present life."
It is hard to see, though, how Rauschenbusch's theology could be called Christian in any meaningful sense of the term. It required no repentance or atonement and carried no fear of judgment or bracing hope of eternal life. He famously denied the doctrine of Christ's Second Coming--with its promise of perfect justice and enduring mercy. The result was a flattened view of the human condition. "It is not possible honestly to confess that Jesus is the Christ of culture," Niehbur wrote in "Christ and Culture" (1951), "unless one can confess much more than this."
The Christian confession of faith, by itself, offers no guarantee that either individuals or societies will be transformed. But, for believers, not even the smallest steps forward can be taken without it.
This is why churches have U2-charest, where Bono music is played and the focus is on starvation in Africa. They have six days to work on the ills of the world, but on the seventh they profane the Lord's Supper ("Do this in remembrance of Darfur?') by ignoring Him. This is why the "Christian" Peacekeepers proudly proclaim that they do not proselytize: They wet themselves over Abu Graib, but don't give a rat's toenail that the place these folks without Christ are going will make Abu Graib look like Club Med.
Read this carefully before you reply. My beef with squishy churches is not the activism; it's that they've become the DNC with holidays and denied the Gospel.