It is not that Christianity is a plagiarist...it is that the most basic and essential spiritual teachings, such as the Golden Rule, can be found in all great spiritual traditions. Accordingly, every great spiritual teacher repeats them, often in virtually identical words. This is as normal and natural as for several different people to say: "It's dangerous to play with fire." or "Two plus two equals four." or "Like attracts like."

I don't call that plagiarism, I call it common sense.