Well the AI isn't terribly aggressive anymore, the odds of him actually losing too early to learn anything at so low a difficulty are infinitesimally low. I think the worst that could happen by picking a higher difficulty is he ends up turteling being boxed in and is forced to look for solutions to get an edge. Which I think is a good way to learn isn't it? Necessity is the mother of invention, same goes for learning.
Also I've heard a lot of people say the lower difficulties are exceedingly boring. It wouldn't help anyone to turn him off from the game as soon as he picks it up.