OK. But he doesn't murder anyone in this movie, either. Justifiable homicide? Certainly. No murder, however.
When we see Lexcorp after Batman has stolen the kryptonite, we see an EMT trying to resuscitate a security guard.
That means Batman has used lethal force while committing a break and enter, against a guy just doing his job, who had every right to use force to stop Batman. If that guy does in fact die, and Batman were to be charged with that crime, he would be charged with murder. If the guy survives, he'd be charged with attempted murder. It's no different from a guy breaking into your house and killing you when you try to defend yourself and your property.
Additionally, in the warehouse fight scene, Batman throws an already subdued enemy into the guy holding the grenade.
The thing about self-defense is that just because somebody shoots at you first, or has shot at you at some point or in some context, it does not give you a license to do anything and everything you please in response (the details, of course, depend on the laws in your area). In court, in order to defeat a murder charge in the grenade incident, for example, Batman would have to convince a jury that the guy he threw at the grenade (the subdued, disarmed, upside down guy) was, at that moment, a threat to Batman's life. Batman would have to testify that the guy hanging upside down made Batman fear for his life.
Then there's Batman's entire pre-meditated plot to murder Superman. So, even if Batman were to defeat all murder charges in those incidents, even if you personally believe that those incidents were all acceptable (which is your prerogative), Batman, as presented in this film, is okay with murder, because he spends the entire film plotting one.