People eat sea anemones and jellyfish, but they would have to be seriously, deliriously, Castaway hungry to eat a coral. Or else corals would have been gone long ago. But, … this does NOT mean coral is without natural enemies.
The coelenterates, corals and their relatives, are very ancient, and in fact may be the oldest metazoans. Proterozoic burrows preserved in the Mackenzie Mountains of Northwest Canada were probably made by animals resembling cerianthid anemones, and are about one billion years old.