Like you said, the police were just following orders. It's their superiors who deserved to be shot, and they weren't there.
Sometimes standing up for "what's right" is not the wise thing to do. As in this case. Of course, a parent should be able to use deadly force to prevent their child from being forcefully taken from them without just cause. But in this case, that would have just complicated things horribly. Since you knew that the people taking your child were not child molesters or criminals of some nature, best to let it happen and then rectify the situation after the fact, in a nonviolent manner.
And sue for the horrible mental suffering you, and your child, were put through. Get some money for the kids college fund. : )
Although I do have to wonder about that phone call from the doctor. Why did that doctor call the authorities? I feel like there's a lot more to this story. The safety of the child should always be put first, is that what was happening here? I suspect the parents aren't as innocent as they would have us believe.