You can't kill them for threatening to take your TV set.

And, as any good mafioso will tell you, dead people don't talk. So if it were legal to kill anyone who threatened to take your TV set, there would be a lot of dead people who allegedly threatened to take TV sets.

Thankfully, in this country, you need to be able to prove that you were in direct danger if you decide to bust a cap in someone's ass. If it were any different, we'd have gun-toters popping off on anyone who walks by their property with so much as a gleam in their eye.