Breakdown of community

If you ask me, Patrick and Lindsay as well as their parents are responsible for the death of these 3 innocent children that trusted each and every one of them. Parents are responsible for their children but there's supposed to be a network that supports the family. I don't understand how Lindsay can supposedly say, to her father, that she has thoughts of hurting the children and he's not like, let's take the kids for awhile, like a long while! I don't understand the decision making of this supposed educated family. Is it really rocket science to understand that a homicidal person should be separated from their potential victims?