Well, LAX is kind of a test case on whether it makes sense to have a hub in an airport you can't dominate. LAX will always be a multi-player market and hence competition will cut into yield.

But if LAX were to be treated like a 'true' hub by DL (which they seem to be not sure about) it's pretty obvious that you need flights to all major cities in the U.S. and you can't ignore them just because they are also "enemy" hubs and heavily contested.