Activate Pirate Ship by tapping it, targeting any creature an opponent controls.
The creature's ability triggers, causing its controller to sacrifice it.
When the creature dies, Pirate Ship triggers, untapping Pirate Ship.
Repeat.
You may repeat this loop whenever a creature enters the battlefield under an opponent's control.
Give Pirate Ship deathtouch, if needed.
Activate Pirate Ship by tapping it, dealing 1 damage to any creature an opponent controls, and destroying it due to Pirate Ship's deathtouch.
When the creature dies, Pirate Ship triggers, untapping Pirate Ship.
Repeat from step 2.
If the effect giving Pirate Ship deathtouch is a static effect, you may repeat this whenever a creature enters the battlefield under an opponent's control.
Results
Destroy all creatures opponents control.
Destroy all creatures that enter the battlefield under an opponent's control.