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I also have seen parents where it was clear that the other parents had no interest in thinking something is wrong with their perfect little angel and have lots of excuses for any negative behavior.

If the other parents are one of those difficult ones, you may also need to start considering protecting your own family/home and never allowing this child around your children or animals, or things you treasure - until you can see clear indications that the disturbing behaviors you see are no longer there.
Agreed.

Childhood cruelty to animals may be an early warning for later trouble. This article mentions possible motivations including "a vehicle for emotional abuse" (bullying/intimidation), and a desire to "alleviate boredom or achieve a sense of control."

Watching adults furtively adds a manipulative aspect to this child's behavior, making the situation more chilling: He seems to be daring anyone to mention what he is doing, thereby casting all who are present as culpable, unwitting accomplices in their silence.

In your own home, proactively stating rules which are clear-cut and objective ("Do not touch, keep your hands to yourself") may be more effective than subjective rules ("Pet the cat nicely, don't be harsh") when working with a manipulative person.