Why believe the bible?

[Amarok]

This is just false, piranhas will cannibalize each other, they tend to go for injured prey, if a piranha becomes injured, they will attack it.

Humans eat each other too and far worst. If piranhas were mindless killing machines they would eat each other all the time sometimes not even to eat just for fun after all their are human who do that . For your assertion to work their needs to be no conditionals to the act .Otherwise human could be consider non moral beings .