Killing another person is a serious thing. Both U.S. and U.K. governments investigate such situations.
In the U.S. most states have Castle Doctrine laws, based on the famous Rights of Englishmen that "Their home is their castle."
In England and Wales, the interpretation of the law has changed to hobble the homeowner more than in the United States.
However, a homeowner in England and Wales still has the right to defend themselves and theirs in their home.
Attitudes in England and Wales seem to be moving toward allowing more leeway for homeowners to defend their homes.
To me, a strange attitude in England and Wales seems to be the desire to protect burglars, thieves, and robbers. (In the U.S., you may not execute someone for burglarizing an empty house, either)
Perhaps Da_Shrimp can comment on the attitude toward criminals in England. It is hard to see clearly from "across the pond".
A famous (infamous?) parody in the United States is a protest sign, saying, "No Mother should have to fear for her son's life every time he robs a store"
The photo above was photo-shopped to create the political parody.