Eastern martial art forms epitomize this "genteel" era. In the western world, it officially ended with the 2nd world war when civilian targets were acceptable, but the ships was sailed already by the first world war.

Of course, we can always go back to pre-civilized societies to justify barbaric behavior.

"Civilized" armies have always been pretty awful to the civilians in places they invaded. Rape. Murder. Pillaging.

Pretty much everywhere, during every war.

I agree, but that's beside the original point. There is a moral difference between raping and pillaging a defeated foe and leveling an entire civilian city as part of a war strategy (examples: Hiroshima, Nagasaki, Dresden, Oradour sur Glane, etc...).

Burning cities is practically a human tradition.

In the pre-World War Western world we were on a massive genocidal race to divide up the lands of those "pre-civilized" societies.