Why do you suppose the fox is protected by law?
They protected alligators until the attacks got bad enougand relented that problem animals could be shot. Do you think a fox learning to eat human livestock is an asset or a detriment to its protected status? No one says kill all foxes on sight, but this animal is causing trouble, and will teach its young to do the same. That won't do its species any favors in the long run, nor will it or its offspring learn to feed itself properly after learning how to get the easy prey. I don't really worry about endangered animals, after all, plenty of species have gone extinct with no I'll effect, and even made room for brand new ones. That's not an excuse to kill off animals, but it does mean you have to value human needs over the animal, when the animal becomes a problem, and this one is.