The GGP commenter was waxing on about having owls in their neighbourhood to such a degree that you'd expect that they'd be interested in introducing owls into a neighbourhood, as an invasive species, for pest control — the same way farmers traditionally introduced "barn cats" as a pest-control measure.

My point is that any invasively-introduced predatory species can and will end up hunting local wildlife to extinction. A species that has never been invasively introduced before isn't suddenly a more "noble" creature. That's the halo effect. One should treat the statement "we should get a pet owl, and let it roam the neighbourhood freely" with exactly the same suspicion as "we should get a pet cat, and let it roam the neighbourhood freely." There will be an equal environmental impact from both.

(And any predator kept as a pet will hunt "for sport", because you're already feeding them, so any hunting they do — and they will hunt, if for "practice play" if nothing else — will be done on a full stomach.)