The Bible needs to be taken literally and in context and one is in good shape. And, there were woes to those who did not follow God's command and wipe everyone out - He wanted them to clean the kitchen of roaches and they didn't so they had to suffer consequences.
RE: OK to believe Sodom and Gomorrah, but not this?
I think what liberals have a hard time with his NOT that God would act on His own to destroy a city and its inhabitants.
It is that God, who commanded people not to kill, would use His own chosen people to actually do 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.
THAT is what disturbs people when they read about it.