No argument from me there. We should help them become better parents, not limit their freedom of choice.
Some parents have no intention of changing. A father who is on meth and who sells his daughter to his drugs supplier should not be "helped to become a better parent". He should be punished and his daughter taken away from him to somewhere where her rights will be better protected.
No amount of liberal "but she'll regret not having her father around", or "but he should be given the chance to redeem himself", or "but her foster parents might abuse her too" is fair to her. People who do bad things to other people should suffer the consequences, and their victims should be given the opportunity to have their rights respected elsewhere.
And people who smoke in the car with their children are abusing them, because they are selling their children's future health for a nicotine fix.
That's a very strange view of the law you've got going on there.
Very few people murder other people. But that doesn't mean we don't have laws to prevent it. And it doesn't mean that we're treating everyone as a murder suspect.