There is a readiness in this country to kill animals whenever they appear to be causing a 'problem'. Be it foxes, badgers, deer, mink...out come the animal assassins. It's appalling, and doesn't show us in a very good light. I haven't watched the link, but I am imagining what happened. And Mere is quite right...a tranquilliser dart could have been used. But of course...it's only a cow.
What's going to happen when this country is totally overcrowded with people, and problems start to arise....will the assassins come out and begin to kill a few off? Killing is the easy option.