The site linked above asked the question. I answered.
How feral cats affect wildlife is made irrelevant when one considers it is inhumane to subject any domestic animal to abandonment in the great outdoors. It should be evident to everyone 5000 years of a symbiotic relationship has evolved them so much they are now a species dependent on us. So much so the biologists say they threaten the very survival of their parent stock through inbreeding.
I would no more loose a cat into the wild to survive than a poodle or pit bull, their canine (wolf) equivalent.
Should one wish to argue abandoning a domestic pet into the wild is not morally, ethically, and humanely abhorrent I would then ask how they could dare inflict an alien predator onto our native wildlife?