Jesus’ basic justice agenda was simple living, humility, and love of neighbor. We all have to live this way ourselves. From that position, God can do God’s work rather easily. Unfortunately, even many who claim to follow Jesus have deviated from this path.
In almost all of history, the vast majority of people understood the “view from the bottom” due to their life circumstance. Most of the people who have ever lived on this planet have been oppressed and poor. But their history was seldom written except in the Bible and in recent books. 
This relatively new thing called “the middle class” gives many of us just enough comfort not to feel the pinch or worry about injustice for ourselves. Many of us in the Northern Hemisphere have a view from the top even though we are nowhere near the top. Many Americans can afford to be politically illiterate, rarely vote, and be terribly naive about money, war, and power.
Only by solidarity with other people’s suffering can comfortable people be converted. Otherwise we are disconnected from the cross—of the world, of others, of Jesus, and finally of our own necessary participation in the great mystery of dying and rising. People who are considered outsiders and at the bottom of society—the lame, poor, blind, prostitutes, tax collectors, “sinners”—are the ones who understand Jesus’ teaching. It’s the leaders and insiders (the priests, scribes, Pharisees, teachers of the law, and Roman officials) who crucify him.
Power invariably coalesces and corrupts. After Jesus’ death and resurrection, the first Christians went “underground,” meeting in the secrecy of the catacombs to avoid persecution. During this time, the Church was largely of the poor and for the poor, sharing resources equally.
When Constantine made Christianity the established religion of the Roman Empire starting in AD 313, the Church’s interests also started becoming imperial interests: power, money, status, control. Once aligned with power, it’s hard—if not almost impossible—to let it go.
Brian McLaren is not afraid to say directly that it is time for us to acknowledge Christianity’s past fraught with imperialism and colonialism:
About forty years before 1492, Pope Nicholas V issued an official document called Romanus Pontifex . . . which serves as the basis for what is commonly called the Doctrine of Discovery, the teaching that whatever Christians “discover,” they can take and use as they wish. . . . Christian global mission is defined as to “invade, search out, capture, vanquish, and subdue” non-Christians around the world, and to steal “all movable and immovable goods” and to “reduce their persons to perpetual slavery”—and not only them, but their descendants. And notice the stunning use of the word convert: “to convert them to his and their use and profit.” 
In addition to this doctrine, selective use and interpretation of the Bible was used to justify slavery for centuries. Scripture is still used by some today to exclude and judge LGBTQIA individuals, even though Jesus said very little about sexuality and a great deal about other things we conveniently ignore. How could we have twisted Jesus’ example and teaching into something so inhumane and unjust? But we did.