It would be okay for you to get upset about that if you were willing to build and maintain the fence at your cost and pay rent for the ground that the trees steal moisture and nutrients from. The hedgerow is the fence and him removing it is no different than him replacing an old barb wire fence with a new one. Would you want to build and maintain a fence in a tree row?

There should be a setback from the property line equal to the height of the tree.  No reason for a neighbors trees to be allow to steal from their neighbor.