my two bits:
I believe in personal freedom. To many of us in the US it is one of our most important principles. So I am always hesitant to support something that forces someone to do something. However, when children are involved issues become a lot more complicated. On one hand, it seems like a parent should have the right to choose what they personally feel is best for their children. On the other, children can't protect themselves and parents may not always make the most intelligent choice for their children.
Finally, as harsh as it may seem, I have to say I fully support the doctor here. TheBoost had a very good example when he said that he'd be angry if his pre-vaccinated child caught pertussis from an infected child whose parents refused to get him vaccinated. Pertussis is an extremely serious upper respiratory infection and is highly contagious, and worst of all, it can have permanent debilitating effects on your child. We don't typically get pertussis or often hear about it... because thanks to modern science (wooo!) we have vaccinations against it. We don't live in the middle ages anymore, there really is no reason to leave your child unprotected and vulnerable. The doctor is just being responsible here, much like schools that require vaccination records before they'll enroll students. Unfortunately, we can't always protect children from the stupidity of their parents, but we can do everything in our power to protect the children of those parents who are doing everything they can.