The Golden Age Superman killed, too. But I think you have to look at it in the context of the time. In 1941, it would have looked really bad to say to kids, “You should never kill whatever the justification”, when you were just about to send a million men overseas to do just that. There’s a panel OneCreator posted above that sums up how we wanted people to think in 1941:
“Much as I hate to take human life, I’m afraid THIS TIME it’s necessary!”.
That is how we wanted people to think in 1941.
So I’m not sure when the shift specifically happened, but let’s generically say the “silver age”. That’s a time where the world’s consciousness was different. In the real world, people were on the streets protesting at the government sending men overseas to kill others. At the same time, Batman’s character changed to someone who would no longer kill, no matter what the provocation.
So Batman reflects the time he was written in. Today, Batman seems reasonably happy with killing again. What does that say about our time?
What you have to ask yourself (punk ) is what kind of time do you want this to be? If you’re cool with your heroes reflecting a “kill or die” “war mentality”, then your heroes will act like Batman did in 1941. If you hope the world is better than that now, then your heroes will act like Batman did in 1961.
My personal feeling is that if we’re not in a better world than we were in 1941, then what were those million Americans fighting for?