Quote from paladin;788261:
Youd be surpised at how much relationships stop you from doing
No one in my life just yet that I care about enough.
If I to make a CARE-O-METER, very few people qualify for me risking myself (personal belongings, money, low levels of danger) for their well being, and no one qualifies for me risking myself (high levels of danger, life, limbs, etc).
I'm quite a coward to be frank, but I find no shame in the fact that I would save myself over someone who was going to die anyways. My reasoning is pretty strong and it would take a lot of emotions to sway that reasoning.
I can see myself having someone like that maybe in the future, perhaps a wife or kids. But really, right now, no problem shooting everyone I know if they were bitten. No sentimental crap either. The longer you give them the more dangerous they become, not as a zombie but as a human.
In a zombie scenario the most dangerous enemies are always other humans. Humans are (arguably) intelligent, but more importantly, unpredictable. If you let the idea of becoming a zombie sink in to their head, or let them pick up on your intent to dispose of them, you don't know what they'll do. They might even attack you, clinging to a false sense of hope that they won't be zombified, trying to defend themselves. They might let their emotions enrage them and try to take you with them. You really never know what crazy thing they'll do.
Its also a danger to yourself because the more time you think about it the more irrational you become. Choices like these should be made BEFORE they're needed to be made, and then you need to follow through on that choice without thinking about it. I know I said I don't care enough above, but I honestly don't entirely trust my own will power. Basically, you have to make choices for difficult decisions while you're still able to think rationally, and then do it the second the situation arises, so that your emotions don't get the better of you. You can reflect and remorse after, but you're going to be alive.