The difference is that the assertion was made that Batman doesn't kill.
With his constant reckless freewheeling through town blowing shit up, this Batman obviously doesn't care so much about that rule, except with the psychopathic mass-murdering villain is in his sights.
Most "superheros" say that and comic book fans honestly believe these guys fight villians while tearing up entire city blocks in which no innocent bystander ever gets hurt by falling debris. It's like having cops in a shoot out with robbers and not expecting a random bullet to ricochet and hit somebody innocent by mistake. That's real life and it happens. How many people do you think Storm killed in X2 creating those hurricane funnels to escape the fighter jets?
Batman doesn't kill purposely
. We have to accept in real world believability that random people on the sidelines or henchmen do get hurt or killed.