Ahh, very funny straw man. What would happen should the property owners not relinquish their land? Eventually it comes down to force and you know it as well as I. So take your straw man elsewhere because it ain't working here.
Here's the rationale straight from the man. Governor Haley Barbour Statement on HB 803 Veto.
From the Bill of Rights of the United States Constitution to the original State Constitution in 1817, the taking of private property for public use has been recognized as an undesirable but necessary power for the good of the citizens. The Fifth Amendment of the U.S. Constitution contains federal provisions relative to the taking of private property.
Before private property can be taken by eminent domain under the Mississippi Major Economic Impact Act (MEIA), the State’s main program for recruiting large job creation projects like Nissan and Toyota, approval has to be given by several government entities.
He painstakingly "fenced in" the use of eminent domain in this process. IMO, he convincingly makes the case his approach was better than the bill given to him.