I've had a couple of situations, even as a resident, where I've "fired" patients...I use that term extremely loosely because what really happened both times was I made the parents so mad that they didn't want to come back - but that's what happens when the very first thing you tell me when I walk in the door is that the MMR vaccine was responsible for your autistic child...
I'm with Stitch. If a child comes into the unit, I'm not going to bat an eye about vaccine status - it's just not a priority at that point. But in my continuity clinic, I frame my interaction with parents as "we're a team that's going to watch your child develop and grow as healthy as possible" and with that, I'm putting the needs of the child at the forefront and letting that guide my decisions. If a parent refuses vaccination then I find that completely at odds with that paradigm.
I know it would violate HIPAA, but sometimes I wish I could just take parents on a tour of the PICU when the kid with pertussis shows up and has to go on the vent for a week, or show the asthmatic who got influenza and ended up on ECMO.