[alt text: an illustration of a person with a head-empty expression on their face, who is saying, "Not letting your cat outside is CRUEL!" Around the person are various gruesome scenes of different cats in distress. From the top and going clockwise, the scenes include: a cat being carried away by a hawk; a cat that is on fire; a dead cat in the road that has been run over by a car; several dead kittens; a cat that is missing an eye and various patches of fur; a cat that is feasting on a songbird; and a cat that is being carried away by a coyote. The person appears to be completely oblivious to these scenes of distress.]
Agreed. The "feral" (shed cats) that we take care of (and fixed)... They've killed all of maybe 12 animals in the past 8 years that we know of (maybe 10x that for shit they've killed that we didn't know about). The correct answer is that number would be thousands of critters... but isn't because we give them cat food that's available to them at will. It also stops them from roaming outside of the "local" area.
The large population of cats together can do a bunch of damage. Feral cats likely do a hell of a lot damage. But claiming that letting a single cat be outside is the end of the world for the local critters is crazy.