I took Batman's "one rule" to be "no killing if there appears to be another option." There was no other option to stopping the garbage truck driver in the heat of the chase nor the nuke truck driver at the end of TDKR. There *was* a non-lethal way of stopping the Joker when he was standing in the middle of the street and it played out by him getting captured.
Cops and soldiers kill but in the line of duty. So killing when appropriate doesn't suddenly make someone the Joker and Ledger Joker knew this. He wanted Batman to completely cross over into becoming a killer out of hatred, flippancy, or revenge. And that was the one thing Bruce would never do, and never did do in any of the movies.
Cops and soldiers kill but in the line of duty. So killing when appropriate doesn't suddenly make someone the Joker and Ledger Joker knew this. He wanted Batman to completely cross over into becoming a killer out of hatred, flippancy, or revenge. And that was the one thing Bruce would never do, and never did do in any of the movies.