I will make the wild assumption that they still love their children. Unfortunately, they have made something else more important in their lives, namely their love for their own personal god who they think demands them to shun unbelieving children. The saying "if their is no god than anything is permissible" should really be 'if you believe in god anything is permissible"
This is certainly not an excuse for unloving behavior. I hate hearing the stories of what we all have had to go through as ex dubs. It is only when we truly understand why people act they way they do that we can make meaningful attempts to help correct their step.
pbrow