Immediately after dropping the Batman v. Superman Trailer, many began speculating, "Did Batman Really Kill Someone in the Batman v Superman Trailer?" I would like to begin by saying that there are Three Major things to think about while watching this Trailer.
The first reason is the obvious reason. Warner Brothers has gotten smart. Yes, we have had awful Movies by Warner Brothers in the past (Green Lantern, Superman Returns), but now they are smart. They have realized that if they have these icons, the one things fans want to see is that Batman doesn't kill. You may ask, "Well in this universe doesn't Superman kill?", and to that I would have to answer no. Yes, Superman killed Zod because he knew there was no way of stopping him; no prison (not even the Phantom Zone) could stop him, and even as soon as Superman killed Zod, he realized that killing killed himself emotionally, and I believe will create his vow to never kill a human-type person again. Now again, you may ask, "Well what does Batman not killing have to do with Superman killing Zod?", well everything. Batman says in the trailer that he has been in Gotham for twenty years, which leads us to believe that he had to have been the Batman for nearly twenty years; and if Batman has been Batman for that long then he may have already killed once as a younger Batman and made his choice to never kill, or just decided right off the bat to never kill. And now, Warner Brothers is at an advantage; they don't have to show Batman kill, and the ramifications of him killing (which killing is a huge backlash of Man of Steel to many fans), they can just get right to the point and have him never kill, which will leave fans of the Caped Crusader very happy.
Reason number two is a reason many fans have theorized about, and that is that the scene is a dream. Now, this in my eyes would most likely be a Superman dream sequence similar to the one in Man of Steel. Superman sees Batman killing these people that for some reason seem to be his guards (I believe these Guards are a thing Lex Luthor set up), and therefore gives Superman even more motivation to go after Batman.
And finally, let's look to a major inspiration of this movie, Frank Miller's "The Dark Knight Returns" graphic novel. In this book we get a look at a Batman that is completely fueled by his rage; He will stop at nothing to hurt these evil criminals. In one sequence in the book, we even see Batman****SPOILER ALERT**** break the Joker's neck without killing him which again shows that his years of training have taught him how to do so.
Well these are my major reasons for why Batman won't kill anybody in Batman v Superman Dawn of Justice. Comment below and let me know what you think!
Batman v Superman: Dawn of Justice, starring Ben Affleck, Henry Cavill, Amy Adams, Lawrence Fishburne, Jessie Eisenberg, Holly Hunter, Gal Gadot, and Jason Mamoa hits theaters on March 25, 2016