It's a little more complicated. First, separating parent and child is an intrinsic harm in and of itself, so you need to be damned certain the parents are harming the child. In this case, the child was already under a physician's care. It's not as if the parents were giving her black market medical treatments. Neither group of doctors claimed that there was nothing wrong with her or that the parents were actively giving her something to make her sick, they just disagreed on the diagnosis.
Essentially the parents were "abusive" because they believed the doctors at Tufts rather than the doctors at Boston Children's.