If WalMart is the ethical business it claims to be, then simply making them aware of the Alabaster situation should be enough to make them pull out of the deal and thus collapse it. Makes you wonder why they haven't. You're right, though. This sort of abuse of eminent domain is widespread. Ft. Wayne, IN has done the same thing with its Southtown Mall. If it's good for the city and economic development, and therefore taxes, they'll just take it.
When you're running a corporation, ethics means operating within the existing legal structure to provide the maximum benefit to your shareholders. That's what Wal-Mart's doing (and rightly so).