The bat man had many chances to kill the joker but didn't and I think he didn't want to kill him because he likes going out there to go and put him be hide bars. They say that batman doesn't like to kill people so that's a reason for not killing the joker and saying that the batman is selfish. Batman thinks that if he kills someone than he would be called a criminal. They talk about the deontology and how it is in the contract and saying that you do not kill so that makes batman not kill anyone also. So after all of that, I think that batman shouldn't kill the joker because he would have nothing else to do and now he has to keep everyone safe.