In the Static Shock/Superman: The Animated Seriescrossover "Toys in the Hood", despite Superman helping Toyman's robot girlfriend hide from Toyman, after her self-destruct sequence is initiated by Toyman (after she betrays both Superman and him), Superman shows no concern whatsoever about her death. This is jarring, considering how far Superman will go to save even Lex Luthor. He'll grieve if he thinks Lex is dying, is a very strict vegetarian in several incarnations, and indeed was hesitant to kill Xenomorphs in a crossover with Aliens! He's frequently had a double standard with regard to non-biological life, though; see his lack of concern for the Bizarros.
This is also pretty bad compared to the Superman episode where the robot girlfriend is introduced. The Toyman doesn't want to take over the world or destroy Metropolis; he just wants to get his property and get out. However Superman treats her like a human being, going to the Toyman's lair to rescue her. By the time he catches up to her and teams up with Static though, she's just a robot.
On the other hand, Superman of the DCAU shows every once in a while that he has no problem being a Jerk Ass when he feels he needs to be. Like the Parasite episodes... He doesn't get any in Justice League, but he makes up for it in Unlimited.
It's not that he doesn't care about Bizarro; Bizarro's too misguided to cause anything but harm on his own and is easily manipulated, so it's best to keep him away from Earth. And Bizarro was shown to be perfectly happy on his planet. He had a carefully-built (for him, anyways) rock Metropolis filled with rock people he interacted with, and when he wanted to be a hero, he rolled a boulder at them so he can stop it. And after a hard day of protecting the rock people of Rocktropolis, he went to his 'Cave of Alone-ness' to watch his rock TV with rock Lois on his rock couch. Oh, and play with his vicious alien creature... er, 'cute doggy' Krypto.
Said White Aliens are the reason the Green Martians are down to one.
Mentioned somewhat in one episode where Martian Manhunter is admonishing Wonder Woman for being too aggressive lately. He brings up an incident against alien invaders, and Wonder Woman angrily replies that they weren't innocent, they thought that humans were food.
In "Growing Pains", Robin befriends a lost, amnesiac little girl he names "Annie". The child turns out to be a portion of Clayface that has gained sentience and an identity of its own, and in the end is re-absorbed into the main body of the villain, effectively "killing" the girl as a separate person. Robin reacts as if she were always a separate being:
Police Officer: We'll book him on the robberies and B & E, right? Anything else? Robin: Yeah, murder.
In "Chemistry", Bruce Wayne is briefly engaged to a woman who turns out to be a plant clone created by Poison Ivy who he has a very emotional romance with. Bruce and many other wealthy people had been subdued by their new wedding partners through the effect of pheremones and the like. However, once it was revealed that these people - who behaved like thinking, feeling, speaking creatures - were not human, Batman and Robin kill them all. Sure, they were evil, but if they'd been human con artists the story would not have ended that way.
Alfred: It would appear, sir, that it would prefer to sacrifice itself rather than allow innocent lives to come to harm. Somewhat like you. Batman: It seems it was more than wires and microchips after all. Could it be it had a soul, Alfred? A soul of silicon, but a soul nonetheless.
In the aptly namedBatman Beyond episode "Terry's Friend Dates a Robot", a highschooler orders a sentient robotic girlfriend from a roboticist. He specifies that he wants her to love him unconditionally and be 100% (aka fanatically) devoted to him. He enjoys the popularity having an attractive girlfriend brings him, and begins hitting on other girls right in front of her. This obviously makes her jealous and she becomes possessive of him to the point of attacking people who either threaten him or her claim on him. When he calls her out on this, she pleads with him saying he is the only reason she lives and that she was only doing exactly what he had her programmed to do. He proceeds to break up with her anyway, giving an insincere Let's Just Be Friends. She is so angry and heartbroken she is driven to suicide. The show treats this ending as humorous and the main characters share a laugh.
Applied thoughtfully in The Zeta Project. The title character, Zeta, is a robot who gains a conscience and decides not to kill anymore. With time, it becomes evident he's his own person, with opinions, thoughts and knowledge he was never meant to have, and he's learning from the world around him much like a child would. The problem is that the agency that created him doesn't knowbelieve he's sentient now; they think he's been reprogrammed. They treat him like a dangerous weapon. Zeta's friend Ro, however, treats him as a normal human being, since she's realized he's just a sweet, harmless, very very very innocent guy.
In the initial arc of Superman: The Animated Series, a bunch of Starfish Aliens stumble upon Brainiac's ship, reactivate him and get swiftly slaughtered for their troubles. Only their silhouettes are visible at that, but their bodily fluids are spattered all over a wall. Nothing even remotely as graphic ever befalls humans. Brainiac himself, by the way, is also fair game for Sups to kill. Then again, this is more because destroying his body doesn't ensure that he's truly dead.
In a few episode commentaries (e.g. "Heart of Steel" and "Read My Lips"), the creators note that the network would let them get away with a lot more graphic violence if the target was nonhuman (e.g. the robots in the former or the Scarface dummy in the latter). They gladly took advantage of the opportunity.