Anyone who speaks English should not confuses figures of speech with metaphors. The Bible is not merely a book of metaphors. It is literal literature that uses figures of speech.
The author is on dangerous ground and does not know it.
I think what people who take this literally have a hard time with his NOT that God would act on His own to destroy a city and its inhabitants. He obviously has the authority to take ANY life, since He is the giver of it.
It is that God, who commanded people not to kill, would use His own chosen people to actually commit the mass killing.
Killing is a very ugly thing ( an understatement ) to do and affects not only the one who is killed, but the killer’s own soul as well. One can never be the same when one kills another human being ( much less many human beings ).
THAT is what disturbs people when they read about it.