I don't think it is thin privilege so much as it is health privilege. I suspect store clerks avoid people with anorexia, too.. I also suspect the discrimination occurs because people perceive weight as being directly under a person's control.

Therefore, if a person isn't controlling their weight, what else are they not properly managing in their life?

I agree that we should not discriminate against people based on any reason but their own behavior, and I think you made a good point in your article about thin privilege and about the Fat Positive movement. Thanks for writing it!