What Constitutes an Unfit Parent in the Eyes of the Law?

Abuse or neglect. Unfortunately the law is enforced by people that have different determinations of what they will let slide or enforce. CPS took two of my four kids because
They did not like my boyfriend at the time and they said my kids acted up too much for me.
Yet I see CPS workers "work with families" where the mom and boyfriend do and sell drugs,
Leave their kids filthy, leave the house filthy, don't feed them well because they use their food stamps for drugs and scream and cuss at their kids and even smack them around.