I think Haidt uses the elephant because it shows our lack of control. The elephant (automatic reactive thinking) is big and will do whatever it wants, regardless of what the rider (controlled conscious thinking) wants. However, the rider is intelligent and can convince the elephant to do what he wants, if he learns how the elephant works. Using an elephant shows that our conscious thought is relatively small compared to the rest of our systems. This shows that we think we are in control when in reality we are not. It also shows that both the rider and the elephant are going in the same direction, practically unstoppable. In other metaphors, conscious thought is a kind of engine that can be strengthened so as to have better control over other systems, but as we know, this is not necessarily true. With the elephant, we can see that we don't have as much control as we would like to think, but it also illustrates Haidt's other point that we are one whole, elephant and rider. It shows that it's less about control and more about understanding and acceptance. So in conclusion, yes, I think this is a good metaphor that illustrates Haidt's points