In the case of a fox, it's called preventative measures. It's not a case of IF it will become a problem that will require disposing of the animal, but WHEN. It is far easier to dispose of it when you see it than it is to try and track it down after it has already destroyed an entire hen house, killed your cat, gotten jiggy with your dog (leaving it mentally unstable for the rest of its life), and dug a trench under your "security fence", leaving you with several thousand quid worth of damage that you KNOW it will return and repeat as soon as you've fixed everything.
So yes, when you see one in the proximity to your property, it IS a valid target. Just like coyotes, wild dogs, crows/ravens are around here.