This discussion is really classic. Knight apparently has a limited understanding of moral relativism and doesn't realize he and Bob are espousing a form of it.
The idea that it is "okay" to purposefully cut down civilians (infants, children, women, elders) in their homes and villages "because it's wartime" is reprehensible to me. I can't believe it's seriously being defended. But of course, it has to be defended, because it is recorded with approval in the Bible and therefore -- according to the narrow interpretive lens some people unfortunately believe is necessary -- it must be okay and morally justifiable.
If these Christians believe it's a crime to kill children, except when it's war time (and then it's okay to cut them up with swords), then they seriously undermine their own moral standing when they condemn those who support another conditional argument that it is sometimes okay to kill children -- in the form of abortion. The chants of "baby killers" are coming back to haunt this lot!