Having been in the position of the farmer in your tale, it is probable that he would have been more than totally exasperated.(My mate said that he was totally exasperated with her when she let the unleashed dog through the gate after reading the warning notice!)
When you devote your life to the welfare of animals, you don't want to be forced into making the decision between shooting someone else's animal and allowing it to continue to damage your own animals and profits. It's a dreadful place to be and it feels entirely unnecessary when they wilfully ignore a sign.
Edited to add: Sorry, Colin, it's (hopefully) obviously not a poke at you as I think we agree anyway, it's just that particular experience is a little, shall we say, raw for me.
kids can be so cruel!
I'm not sure if the this is about my comment regarding folders, but if it is I'm honestly not deriding them. The story about the cross bar is absolutely true. The fact is my folder was a girls bike, well a womans actually, it had been my mums, but owing to the fact we lived in a cardboard box and ate gravel for tea I had to put up with the hand me downs (fortunately this didn't extend to my mothers clothes too!) You'll be pleased to know however that despite the scaffolding tube a quick piece of sugery with a hacksaw through the middle of the tube meant it could still be bent in half, so a folder it remained, just a boys one 
