The Good Samaritan

I've never really understood the parable of the Good Samaritan.  It's a Sunday School classic, and is generally (I believe) used to make the point that we should be nice and help people, even people who are different to ourselves.  A good principle, but surely not what this particular parable is about.

Context.  Luke chapter 10.  An expert in the law asks Jesus how to have eternal life.  Jesus tells him to obey the commandments 'love god, love your neighbour'.  The guy asks 'who is my neighbour?', so Jesus tells the story...
A man was going down from Jerusalem to Jericho, when he was attacked by robbers. They stripped him of his clothes, beat him and went away, leaving him half dead. 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, brought him to an inn and took care of him. The next day he took out two denarii 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.’


Then Jesus asks 'who was his neighbour'.  The man correctly replies 'the one who had mercy on him'.  Jesus says 'go and do likewise'.  End of the scene.

The first problem is that according to the parable, your neighbour is the person who helps you.  Implying that we only need to love the people who are nice do us.  This is contrary to the rest of Jesus' teaching.
The second problem is that Jesus' story doesn't match the original question he was asked.  He was asked about who counts as a neighbour.  It seems that Jesus (mistakenly or intentionally) gets it back-to-front.  The man asks who his neighbour is, i.e. who he should love, but Jesus describes who his neighbour is in terms of who loves him.  The question put the 'neighbour' in the role of the person to be loved, but the story has the 'neighbour' in the role of the person doing the loving.

It is surely significant that the man's question 'who is my neighbour?' is precede by the phrase 'But he wanted to justify himself'.  The man wants to justify himself.  As a law expert, he may have been quite self-righteous, thinking he was keeping the law and on the path for eternal life.  The question about who is his neighbour could be seeking the answer 'your family and friends' or 'other Jews'.  He may have been hoping for this so that he could say 'go, well I love them, so I'm sorted'.  By getting the man to agree that the Samaritan (historically enemies of Jews) is the neighbour, Jesus shows him that he should be loving all people.
This is quite like the Sunday School message.  But it ignores the difficulty of Jesus answering in a back-to-front manner.  The story changes the role of the neighbour from the one to be loved (in the man's question) to the one doing the loving.  Why?  Is this intentional from Jesus?  If so, what point is he trying to make?