The truth of the matter is that if we ascribe any value to animals at all we should not be harming them at all. Whether or not you consider death to be a harm is not the issue here. I deal with that elsewhere.
It is belief in the sentience of other animals, all other beings for that matter, including humans, that makes cruelty and morality (and immorality) possible in the first place. In this sense if someone can be a decent person and smack an animal (in that action I mean), then someone else can torture it for weeks and be a decent person (in that action). The point is not that these crimes, sins, or wrongs, or whatever we wish to call them are equal, but that if one is wrong then they both are. Harm requires sentience to exist, as a matter of necessity. Morally speaking, any frivilous harm is bad, given that there are agents that experience it.
Most of us do not question human sentience, and the fact of the matter is that are brains are soft wired, if not partially hard wired, to recognize sentience in not only humans but also nonhuman animals on this planet. I imagine we could intuitively recognize sentience in an alien species, but who knows. Either way, separation from this intuition occurs basically as a result of inconsistent and laughable abstracted arm chair philosophy, if we can call it that (philosophy). The bottom line is that no one actually lives based on these precepts except when they are being inconsistent and/or psychopathic.
It is a pretty simple idea, but it separates what a vegan is trying to achieve from just about everyone else.