"If parents of an ED patient are dysfunctional then that must be part of the reason for the illness."
No, sometimes parents are dysfunctional and their kid develops an eating disorder. And that REALLY sucks for all of them. Parents who are bad at parenting, mentally ill themselves, or genuinely bad people aren't as likely to be great caregivers. This should surprise no one.
Yet somehow this has gotten tied up with the idea of cause and meant that all the perfectly average and even stellar parents live under a cloud of suspicion. There is a dogged conviction that the majority of ED families are dysfunctional when that is clearly the exception. People cling to these ideas with an evangelism that is frightening, as if questioning it means one is condoning abuse and the torture of kittens.
If you suck, then cause is assumed and let the games begin. And if you seem normal? There's an answer: you're TOO perfect or we need time to figure out what you did to "contribute to" your child's life-altering deadly disorder.
Don't kids need good parenting ANYWAY?
Sucky parents aren't good for anyone. And even great parents need all they've got to respond well to this crisis.