It's important to understand that it's a tenet of apologetics that God is perfectly righteous, and therefore nothing he does can be considered evil. Starting with this conclusion, apologists seek reasons to free God from any charges of immorality. I'd appreciate everybody's input regarding their own reasons why God is good despite his murderous ways, but here are some reasons to start with:
- God's killings are actually good, it's just that we cannot understand why it was good for him to kill.
- God is able to kill anybody he wants to, so it's OK for him to kill. His might is right!
- God is the creator of all life including human life, and therefore as the creator of life he can snuff it out any time and any way he chooses to.
- Since God is perfectly just, his perfect justice cannot tolerate sin, and he must eliminate sin by eliminating sinners.
- God kills those he sees as a threat to his "chosen people."
- We Christians invented and own morality, so if unbelievers say God's killings are evil, then they are stealing our morality.