Why is murder bad, though?
Not really going to address your second part (Note -- I mistakenly edited the 2nd part, it basically said that Lot's wife disobeys God, and not Lot, and that's the critical difference), because I mean that's just a difference on how we interpret the Bible and God's law and stuff.
As for murder... I'm going to try to describe this as someone who doesn't believe in religion, so you can maybe see how morality is possible without religion:
When one makes a decision that impacts others, one has to consider two possible variables -- the net benefit/loss that you obtain, and the net benefit/loss that those you interact with gain. The determining of such things is very complex, but we won't need to define it for the final result. One should, as such, strive for as many +/+ actions as possible. This is trivial.
-/+ actions; that is, actions that benefit others at cost to you, are also, mostly, acceptable. However, if the - part is a lot more than the + part, then it's a bad action. If there's a good trade-off, it's a good action if you don't mind the losses.
-/- actions should be avoided at all costs. This should also be trivial. Except, people do them all the time.
+/-, that is, actions that help you at the expense of others... these are the difficult moral cases. Like, should I buy that cheap TV for my own enjoyment knowing someone's life was worsened by making it? This is where it's hard to quantify in a lot of cases....
But murder is not one of them. Murder has a benefit of negative infinity to the person you kill. There is NO gain at all that justifies the loss the other person faces. Period.
That's also where sociopathy is a bit dangerous -- if they don't care about other people, the "-" part will be very, very low compared to society's estimation. They may see such an action as beneficial to themselves when it's really not beneficial to society in just about everyone else's estimation.