In most generic rpgs, most random npcs are purposely written to be innocent victims who the hero is clearly intended to help. If you get off on ignoring that and deciding to murder poor, struggling farmers for no reason besides the giggles, well, I won't say I'm certain about it but if I had to wager on it I'd bet you are an asshole in real life as well. Moreso, since you are posting on RPGCodex.
Now if the game is either entirely for fucking around in like saints row or is shoving in your face what a nihilistic grimdark world it is where absolutely everyone is a degenerate shitbag then killing everyone for lulz or otherwise is just part of playing the game. If anything, it's combatfags who ignore everything else in the world other than what is maximally efficient as defined by the arbitrary game rules (instead of just, you know, cheating) that are behaving in an autistic manner.