There's no point in arguing with them. Seriously the question was worded terrible. Im sure you could interview those same people and begin asking them if they think such and such should be taken literally, just like the sun and shield verse and they would say no. But they being of honest heart do believe that the Bible should be taken literally when possible. Thou shall not kill would be a great example.
Unless of course you are at war with another country, or the state is executing a man, or in defense of your home, etc....
That admonition is so vague as to be utterly and completely useless. You believe it has any meaning? Really? That it somehow separates Christianity from other religions? Christianity was the only religion to come up with the absolutely novel idea that killing other people wasn't a good thing?
The American legal system has vast amount of laws about what constitutes justifiable homicide. It varies from state to state. If legislators consulted the Bible when crafting the laws pertaining to this complex topic, you sincerely believe that "thou shalt not kill" would be in the least bit helpful?
PRO-TIP - The Code of Ur-Nammu which was written more than 500 years before the oldest book in the Bible (Job) had this to say about murder:
1. If a man commits a murder, that man must be killed.
Actually you should take a good long look at it. There are some similarities there with the Bible. These people did not follow the God of the Isrealis.
https://en.wikipedia.org/wiki/Code_of_Ur-Nammu