Granted, I wasn't privy to the process which lead to their decision, but even without being affected as a stakeholder in the outcome, there seems to be a lack of "big picture thinking at play here. For one thing, the industrial zone to the east and south of downtown Los Angeles is a vestige of an age when it was on the outskirts of town... now that same area is surrounded by the urban megapolis. The changes in industrial land use may make the region less feasible for heavy industry than it was a century or more ago. The intransigence of the Planning Department in regard to residential use not only shows a closed-mind attitude for the 21st century vision of the city, it also doesn't take into account that some of the land they wish to "preserve" for industrial space was at one time residential. And no one can deny that if there is a critical shortage of industrial space in Los Angeles, the availability of affordable housing is even more acute. Perhaps the Planning Department has a way for the future workers in the industrial section to commute from Arizona.
As San Francisco, Minneapolis, Miami, and many other cities have found, the areas previously utilized for industry have proven adaptable to high-tech firms, and new ways of comfortably mixing live-work space as opposed to single-use zoning. Given the changes in the Southern California industrial landscape, I'm not sure the Planning Department even has a firm grasp of who the willing industrial users of the area would be --if they still exist at all.
Sam Hall Kaplan, in the March 12 edition of the Los Angeles Downtown News, wrote a brilliant (as always) piece on the subject. As he knows most of the players and the process with both an insider's and a professional and academic viewpoint few others possess, it would do the public officials (and anyone interested in the future of cities) to read his column.
As for the rest of us, get some popcorn and a comfy seat to watch the jousting among the players as this drama plays out.