So many families, ours included, learned to diffuse the escalation of fear/anger/fear between ourselves and our kids by adopting (faking, if necessary) an impassive and unruffled face to ED.
I doubt any parent gets through the experience of supporting a loved one through eating disorder recovery without getting mad. What we're really angry about is how the illness steals our child's intellect and abuses his/her emotions and isolates them in a maze of self-destruction. We're angry at our inability to reach them, and often at the difficulty of finding clinical support. It is more about fear than anything.
Ideally, we learn early on about "externalizing" the illness so we see the thoughts and behaviors as "ED" and not as our child - this diffuses our anger and lets us hate the illness while still loving our child. But anger slips through, driven by fear, and we raise our voice or get sullen or stomp away. We make threats we're terrified to make good on. We strike out at our spouses for being more or less angry at ED than we are.
What eventually becomes clear to many families, and certainly to my husband and I, was that our daughter perceived any negative emotion on our part as anger, and it frightened her. Her fear drove our fear. I've often heard people during their illness speak of feeling hated or looked down on by seemingly benign and caring gestures by families - even the phrase "I'm worried about you" is taken in as a criticism and as anger.
ED puts patients in a perfect box: it blinds the person to declining health, re-frames the concern of others as hostility, and in a perfect coup transforms the patient's own fears into expressions of anger toward those trying to help.
Mothers and fathers are the perfect people to end this cycle, to stand in the stream of terror and anger and return nothing but Buddha-like calm. It works, and often we are more amazed than anyone!