While Jesus was having dinner at Matthew's house, many tax collectors and "sinners" came and ate with him and his disciples. When the Pharisees saw this, they asked his disciples, "Why does your teacher eat with tax collectors and 'sinners'?"
On hearing this, Jesus said, "It is not the healthy who need a doctor, but the sick. But go and learn what this means: 'I desire mercy, not sacrifice.' For I have not come to call the righteous, but sinners."
-- Matthew 9:10-13 (NIV)
The social gospel is not an addendum to the gospel; it is the gospel. If we read the Gospels, it becomes clear that it was not what Jesus said about God that got him into trouble (but) his treatment of men and women, his way of being friendly with outcasts with whom no respectable Jew would have anything to do. It has always been fairly safe to talk about God; it is when we start to talk about men that the trouble starts. And yet the fact remains that there is no conceivable way of proving that we love God other than by loving men. And there is no conceivable way of proving that we love men than by doing something for those who most need help.
... William Barclay