Well, we're talking about a space station that destroyed Alderaan (murdering probably a couple of billion people in the process) and was about to destroy the Yavin 4 moon where the Rebel base was located. So relatively speaking not quite as many voices suddenly crying out in terror before they were suddenly silenced. Besides, he wasn't a Jedi yet, so no Jedi code was violated.
Well the point is, living being or not, if you're on the wrong side he'll kill you. And he was personally slicing and dicing Jabba's goons at the battle of carkoon - even though it looked more like he was just batting them off the skiffs....is there a 'non-lethal' setting for the blade of a lightsaber?