I was just struck my what this reminds me of....
An abused wife defending her alcoholic husband
I've been thinking this too, throughout reading this thread.
I think all the logical arguements and bible background and interpretations of whether the Canaanites deserved it or not mean nothing.
It's all about love.
Like cog says:
It won't matter if God himself rapes and murders every single man, woman, child and animal on this planet and tortures them all for eternity.
I think someone deeply in love can justify anything, and someone's love of God can go deeper than any other love. People still kill for God today.
To quote one of my favourite people "We can love quite well. If not wisely."