Consider Jesus' parable of the Good Samaritan.
"A man was going down from Jerusalem to Jericho, when he fell into the hands of robbers. They stripped him of his clothes, beat him and went away, leaving him half dead with no clothes. A priest happened to be going down the same road, and when he saw the man, he passed by on the other side. So too, a Levite, when he came to the place and saw him, passed by on the other side. But a Samaritan, as he traveled, came where the man was; and when he saw him, he took pity on him. He went to him and bandaged his wounds, pouring on oil and wine. Then he put the man on his own donkey, took him to an inn and took care of him. The next day he took out two silver coins and gave them to the innkeeper. 'Look after him,' he said, 'and when I return, I will reimburse you for any extra expense you may have.' "Which of these three do you think was a neighbor to the man who fell into the hands of robbers?" The expert in the law replied, "The one who had mercy on him." Jesus told him, "Go and do likewise." New International Version
Someone asks Jesus "Who is my neighbor" meaning "Is there a limit on the range of people to whom I have moral obligations?" So Jesus says "OK, imagine yourself having just been beaten up on the side of the road and left for dead. The Priest and the Levite, pillars of the community, walk on the other side. The Samaritan (religiously, racially, and probably morally in the "wrong" group), does help you. Now tell me that the people in the "right" group are your neighbor and the people in the "wrong" group are not your neighbor. All of a sudden the line between "us" and "them" starts to disappear, doesn't it?
Regardless of how you view Jesus theologically, you have to see this as a sheer stroke of moral brilliance.