Did you actually see this happen? Fox attacks on cats are very rare indeed and injuries are much more likely to be caused by other cats or a loose dog.
We've got 6+ foot high fence around the whole garden. There's no chance a dog could get over the fence, attack the cat and then escape back over the fence in the time it's taken me to get outside.
The vet knew exactly what had done the damage and confirmed there have been lots of sightings and attacks in the area.
Both of the cats rear legs had been bitten multiple times and there was no bone damage other than a small chip made by a tooth, larger than a cats. There was no compression wound like a dog would have made. It was a quick, sharp and frenzied attack..
CCTV has gone up and the perp will be dealt with

As for playing god; well I'm afraid man kind has already done this for too long which is why we are in this mess.
Foxes are natural scavengers and only go for small easy meals. The sheer size of some of these animals is the result of constant copious amounts of food left by us for them to eat.
Their population has grown as a result and now the larger animals are moving onto food items their own size.