Many people think that if they accept the term "brain disorder" for eating disorders then they are saying that eating disorders are just built in, can't be changed, and would only respond to drug treatments. This is a common misunderstanding and leads to what strikes me as unnecessary static in the conversation.
Calling anorexia, binge eating disorder, and bulimia "brain disorder" simply identifies the organ of the body affected. It implies that the problem is with the brain and not the environment, which is an important orientation, but that would be like saying that diabetes is not affected by behaviors and does not affect behaviors just because the pancreas is affected. Of course brain disorders are influenced by and influence the environment!
Therapy is one of the ways environment affects the brain. Therapy is a really important element of treatment that most patients need or benefit from - but not ANY therapy. Just as you can't thrown any drug you want at an illness, at any dose, psychotherapy has risks and benefits and needs individualization. Some therapy, in the wrong doses at the wrong times, can be actively harmful.