Isn't there an underlying assumption here of "do no harm"? Why is it wrong to do harm? Who says?
We are social critters. We need each other to survive, because individually we are weak and make a great meal for a goodly number of predators. Plus, individually, we have a hard time procuring that which we need to survive. Because we need to work as teams, trust is paramount. The great ethical philosophies, including those predating Christianity, realized this. The golden rule cropped up independently in a half dozen civilizations simply because it is rational and promotes survival. One did not need to be a God-fearing Christian to realize this.