KN ~
God does command a lot of killing in the OT, yet He also smites and takes life in the New.
these are not a random people, but a people whose hearts were set against God, against His people, and against opportunities to do the right thing.
God does take life, sometimes on a mass scale. God's judgement is tied up with His love, but that doesn't mean that God is always passive or tolerant of sin, wrong, arrogance, and hostility. God doesn't punish people for things they fail completely to understand, but for what they knwongly grasp and then reject or do the opposite of. when the Creator is trying to get your attention, or ask you to help someone out whom he loves and has a plan for, it's a good idea to listen.
and yes, sometimes Biblically God whipes out entire societies and ethnic groups. not because of their ethnicity, but because of who these people are, and what they have decided to do and be.