I know they're pixel people, but I still feel bad when I kill someone off for storyline purposes. I haven't completed the mischief/evil aspirations, though I did try them out once. I just want to be friends with (almost) everyone, become rich, and live out the fantasy.
Even so, if I'm out in public and someone just dies, I'm not bothered unless it directly affects my plot. Why is that? Apparently I don't mind things happening to Sims as long as I didn't directly harm them myself.