I am trying to understand the reason why Leto III merged with the sandtrout in *Children of Dune* and why he was so committed to the Golden Path.

I just finished the first three books and I fear that I have missed the point of why prescience is so bad. According to the [wikipedia entry][1], Leto wanted to teach humanity a lesson to avoid stagnation, so much so that he punishes them for 3,500 years by being a brutal emperor. 

What isn't clear to me is how this actually saves humanity? Given the horrors of Muad'Dib's holy war and Leto's rule you'd think that having a few prescient noblepeople running around wouldn't be so bad. And why does he need to merge with a sandtrout and then let the Sandworms go extinct in order to accomplish this?

I checked out the Dune and Children of Dune miniseries in the hopes that the "made for TV" aspect would simplify the explanation of Leto's commitment but it doesn't do a good job explaining that either, it just seems to be a rehash of Leto's speeches on why the path is necessary.

  [1]: http://en.wikipedia.org/wiki/Golden_Path_(Dune)