Commerce raiding is a legitimate tactic in maritime warfare.
CSS Alabama was commissioned ship in the Confederate Navy, not a privateer. CSS Alabama was acting under orders from the Confederate Navy Department, not a letter of Marque.
That is not piracy. That is naval war at sea. She was no more a pirate ship than any submarine torpedoing a commercial vessel of the enemy. Both the Royal Navy and the French Navy recognized her as a legitimate warship of the Confederate Navy and not a privateer. Otherwise they would have been hunting her down, just as the U.S. Navy was.
That was very controversial in the First World War. Submarines didn't make their presence and demands known in the way that surface ships couldn't help doing.
P.S. The artist Edouard Manet was on the coast when the battle took place and rendered it in this painting.
