There have been a lot of memes made on this quote by Batman, but where or when did he say this line?
If you kill a killer, the number of killers in the world remains the same.
It looks like this quote is falsely attributed to Batman. It is also attributed to Winston Churchill, but there is no hard evidence, that I can find, that either one said this.
It appears someone at some point used a picture of Batman and stuck the quote in front of it. (At least that's what one guy blogged).