How might Piggy's death be equated to the slaughter of the pigs?

The first pig was killed to provide meat, but then the killing became more of a power trip for Jack and his tribe.  When they kill the mother pig, they are foolish because they are killing what could be a future source of food.  Rather than look for another pig, the killing is done because they CAN kill. It is senseless.  The killing of Piggy is senseless, too, for the most part.  Piggy represents intellect and killing him is therefore killing intellect on the island.  In the aspect that it was essential to kill intellect on the island so that the evil could fully emerge, then killing Piggy was essential just like killing the pig for food was essential.