Ants, cockroaches and mice and rats are not the same as the ducklings and anybody knows that. We kill them because they are pests and vermin.
One hallmark of a future serial killer is the killing of small animals, pets, as a child. This is referring to people’s pets, like cats and dogs, not rats and spiders. Although they probably kill those too and get an enjoyment out of it. Whereas when a normal person kills a spider they’re a bit grossed out but glad it’s dead so no one will get bitten by it.
"Purposefully harming helpless animals is the hallmark of a murderer-in-training."The person who made this statement didn't qualify it, and without qualification it states that harming animals means you're going to be a murderer. So anyone who harms any animal according to the quote is going to be a murderer. Total load of cow squeeze. Or maybe in this case duck squeeze.