Snails and worms

Kevin’s new hobby is to pick collect snails and worms and what ever disgusting insects he come across. When has them all in a bucket he feed them with grass and shower them with water. And sometimes he crushes them against the ground. We’re trying to talk him into collecting them and feeding and showering them, but to skip the crushing part. But this is how the dialog goes:
Pernilla: What are you doing?
Kevin: Crush them so they die.
Pernilla: But you can’t do that, it’s sorry for the animals and it hurts on the animals.
Kevin: No it’s not hurting.
Pernilla: How do you know it’s not hurting?
Kevin: They don’t scream!