Well, I too rescue animals of all kinds, and wouldn't dream of posting such a graphic description of such repulsive cruelty to a cat or any other animal when there really are people out there who would actually do just those things that you wrote about .As someone who claims to be interested in animal welfare, I think it is extremely offensive for you to have written it.
Cats, like any other animal, are acting purely on instincts that they are inprinted with from birth....unlike people who have the ability to make an informed choice about most things that they do. It is absolute rubbish to claim that they kill for fun...it is as instinctive in a domestic cat to hunt as it is for a dog to scavenge...however well you feed them.
I have enclosed my own garden with an overhanging fence, so they don't wander into anyone elses garden & they have never in the 15 years I've had cats, killed any birds. If they did, I would hope that being ' higher up in the food chain' as you put it would enable me to use my brain & realise that smashing up another animal is not the way to solve this problem.
I still think there is something fundamentally wrong in the mind of a so called animal lover, who could write what you did.