If I was in the situation those people were in, I'd damn well have a gun with me, every second of every waking moment and I'd probably learn to use it in my sleep, too.
And if I needed to use it, I'd use it, and not particularly care what anyone thought about it.
But for politeness' sake, if it were possible to muffle the sound in some way, I'd do that. No sense in aggravating my fellow survivors anymore than necessary.
But I'm keeping my damn gun. Cold dead hands and all that.
You would of thought Shane would of shot Otis in the head to let him off the pain of being eaten alive.
The debate over that is whether Otis would have made better bait alive than dead. But it's been established that zombies can tell the living from the dead by smell. A freshly-dead Otis will not start putrifying instantaneously. I'm sure he could have smelled alive for the, oh, ten seconds needed to provide a distraction. He might not have even been technically dead (no heartbeat, no brain activity) in so short a time.
Contrast that with the practical problem of a still-conscious Otis fighting Shane for the pack he was wearing and possibly getting both of them killed. If Shane shot Otis in the leg for nothing more than to gain an advantage, that strategy could very easily have backfired. In retrospect, I'd say it was a coin toss which decision was better in terms of effectiveness.
And getting back to the morality of the situation, I've decided that these people are in such a mind-bendingly horrific situation that there's no way to apply notions of morality to what they're going through. Whatever they want to get up to is fine by me.