We have peacocks in our garden and the foxes have had two of them over the years. They peacocks normally roost high in the oak tree, but for reasons unknown to us, on 2 occasions they haven't and therefore fallen victim. Although this makes me sad, I see it as nature taking its course. The fox has to eat, and is not aware that these are pets to us, or even someone's livelihood. I have seen film of foxes that have killed all the chickens in a roost. They may eat some there but then they take them away to bury and store. Of course if they are disturbed during this process, the job will not be completed and it seems that a pointless killing spree has taken place.
I try to stay true to the belief that nature is nature, and foxes eat chickens (and peacocks), just as we eat chickens.