Life in the United Kingdom

You are in your own home, minding your own business and 4 guys break in with a gun to rob you. Afraid for your life you grab a samarai sword you have and stab the guy with the gun. He dies and you are the one who goes to jail - for 8 years.

What's wrong with that picture? Why would you want to live where you can't, by law, fight back against criminals in your own home? That's insane.