Well over 500 years before the philistine coined the popular phrase, a lowly monk from northern India said, "Just as you wish to be happy and free from suffering, so do all living beings, in this respect we are all the same." Another popular monk in India, about the same time as the popular philistine monk, said, "All the happiness there is in the world comes from wishing others to be happy. All the unhappiness there is comes from wishing ourself to be happy." Then another monk, that I'm fond of, said, "With the intention to attain the ultimate supreme goal, that surpasses even the wish granting jewel, may I constantly cherish all living beings."
So what the lowly monk from the Gaza Strip was really saying is to be good to others and good will come to you; wrong to others and wrong will come to you. 
The diamond rule might be Hoods' nature, but that's how lawyers look at things.