I've know that since day 1.
I have never harmed an animal.
No one said you did. But the hatred still exists. And hatred is the catalytic force that can result in harm to a sentient creature.
The cat can't say, 'Ouch. Please don't hurt me.' A small child who is just learning to talk, same story. They cannot communicate their pain and terror in a 'human' way, but they scream it out in their actions. (Both the cat and toddler will scream in a very literal sense of the word.)
Devalue one. Let hatred develop...and the slope is greased. Morality is determined by the individual, but there are certain things that are huge red flags.
The difference between inaction and action pertaining to that hatred is a deciding factor between sociopathy and psychopathy.
Sociopaths do not act on their hatred or indifference. Many actually learn to mask to pass as 'normal', very much akin to autistics.
Psychopaths take action and find malicious delight in the pain they cause.
The difference between inaction and action is huge, but the stigmata holds the two as equals in the eyes of society. (And pragmatically speaking that is not fair.)
Sociopaths lack empathy. A capacity they were born without. It is a safety gauge on behaviour that can have devastating consequences for those dealing with the disorder.
Sociopaths actually make up about 4% or 1:20 of the general population (US) and occur nearly twice as often in the population than autistics (2% or 1: 49).
The Sociopath Next Door by Martha Stout is an insightful, slightly terrifying read on the topic.
A more fundamental question:
How much of a person's hatred for animals is rooted in the animals' instinctual reactions to the unspoken hostility?
For a majority of people, animals (our pets in particular) respond with joy and friendliness when they see us. But when that reaction doesn't happen because of a vibe the animal picks up on, that affection and attention is withheld. The animal deems that individual unworthy and that can trigger an unconscious hostility because of the animal's instinct based reaction.