In the U.S., walls are often prohibited because of zoning regulations. When I pinned down a local zoning expert on why walls were prohibited, it was not for esthetics or crime control. It was so zoning officials can see what you are doing on your property.
Zoning is all about power. The Mayor, in this instance, is just showing that he has more power than his neighbors.
Villaraigosa, like Obama, has a radical leftwing history (as outlined in my post) and is motivated from similar ethics, values and instincts. Villaraigosa's wall has nothing to do with your simple neighborly competition interpretation. You better learn from the history of these radical "leaders" before it's too late.
Using government to control what you do with your property for their benefit.