I think we tend to view Jesus' Golden Rule as nothing spectacular, but rather simply a matter of commonsense. In seeing it that way, I believe we largely miss its real significance and force. The implications of really embracing and practicing this injunction are actually quite mindboggling and downright counter intuitive. By counter intuitive I mean decidedly not what we would judge to be commonsensical.
Too often, I believe, we narrowly view the Golden Rule as solely guiding our personal actions toward those we immediately interface with day to day, our family, friends, and close associates. However, I see no justification for thus limiting the scope of Jesus' words. You will notice that Jesus states no limit on who should be treated as we would like to be treated. It applies to everyone. This is especially emphasized in the story of the Good Samaritan, where the hated Samaritan is identified as a neighbor.
When this universal applicability is recognized and honored, then our sense of commonsense gets stretched a whole lot. Suddenly I must consider how my attitudes, speech, and politics affect the lives of others around the world and whether these more subtle aspects of my behavior result in their being treated as I would want in their particular circumstances. In this view, it becomes difficult to divorce my personal treatment of others from the group policies I promote in politics, religion, economics, education, etc.
We may choose to ignore the Golden Rule in formulating and enforcing public policy, but I don't see how we can do that in the name of Jesus. Some may conclude that truly Christ-like public policy must await some future establishment of a utopian earthly theocracy of some sort. Even if that is the case, I don't see why that is an excuse to ignore the words of Jesus in the meantime. If the greatest commandment was not immediately applicable in all its aspects, why not say so.
No, in my personal experience, the real reason we tend to redefine and limit the words of Jesus is because they are just too challenging to our commonsense. Jesus apparently wasn't into commonsense; he proposed "uncommonsense", instead. When presented with a list of commonsense reasons why this or that is right and true, we shouldn't cite Jesus in support thereof.
No one says that going against our notion of commonsense is easy. It definitely involves a large measure of faith. Of course, faith is extolled in Christianity anyway. However, I don't believe that that faith is an undying adherence to the many "commonsense" principles and assumptions so often claimed as inviolable and even divinely ordained.