As I understand it, the whole 'zombies eat living flesh' mythology stems solely from the 1968 Night of the Living Dead film. Prior to that, zombies were pretty much only the murderous undead with no eating, or the Haitian voodoo zombie.
Again, something else that doesn't make sense. If they eat ostensibly because they're hungry, then why would they stop once their prey stops moving? Is there some sort of special 'zombie sense' they possess that stops them feeding on each other?
While I'd be hard pressed to think of anybody who wouldn't agree with killing a rabid dog, I think we're moving away from your 'reluctance to kill' scenario and more into the 'are you physically capable of killing' area.
Having been attacked by a pack of dogs while unarmed, I can attest it's harder than it sounds to avoid being bitten, but since humans aren't designed to use biting as a primary attack, it's a somewhat different scenario.
As for the hesitancy, I would agree that most would be hesitant, but for an entirely different reason - how to attack it without being bitten, rather than a reluctance to kill.