Little guy says “No” to the big guy, and a wail of anguished doom rises from an industrial giant.

“BATON ROUGE, La. — It was a squabble over $2.9 million in property-tax breaks — small change for Exxon Mobil, a company that measures its earnings by the billions. But when the East Baton Rouge Parish school board rejected the energy giant’s rather routine request last month, the “no” vote went off like a bomb…