How on earth do people know the parent hadn't given permission for the childminer to smack the chil ? They are well within the law to do so, it is only illegal for a teacher or staff member in a nursery setting to smack a child, even with the parents permission. Staff privately employed by parents, such as a childminder or nanny can be given permission to smack a child by the parent.
I do not smack my children, I am perfectly able to discipline them without smacking. However, if parents chose to use smacking as a method punishment, and are doing so within the law, that's really none of my business.
This child minder may not have even smacked the child, and what one person classes as 'dragging' the child in by her arm, another may not. Even if the minder did slap the child's leg, I wouldnt' necessarily class that as abuse, nor would I say it means the child is at risk.
I think people need to keep some perspective on this and not allow their personal views on smacking to cloud their judgement. The fact is, reporting could ruin this persons career, and whilst that is not more important than a child's welfare, it is surely a factor? The woman could be totally innocent of any wrongdoing!
Personally, I would keep an eye/ear out, I am sure parents would notice if there was something really wrong with their own child.