A BUCKET OF ASSHOLERY

[Cutz]

which is probably why the grandfather and his girlfriend were charged with child endangerment.
My post, however, was questioning Cutz statement that the parents are ultimately responsible.
When the dog we adopted from the shelter bit my grandson a couple of months ago, I didn't blame his parents for letting him come visit us, I blamed myself for not knowing what kind of temperament the dog had before allowing my grandson near him.

The parents are responsible. You may blame yourself for letting your grandson get bit... but you weren't charged with a crime for endangering your grandchild either... I'm assuming. The fact that those grandparents were shows a lack of care on their part and a lack of judgement on the parents part for leaving the girl with them.
Also, whether or not you blame yourself for your grandson getting bit, his parents will first and foremost blame themselves for putting him in that situation. Objectively, responsibility can be shifted around from the child, the parents, you, the dog, the previous owners of the dog, the shelter, lots of people... but when it comes to caring for a child, parents ultimately foot the bill. Fair or not, that's how it is.