I'm not sure if this is the correct forum for this post, but here goes...

Several years ago, I was enrolled in a psychology course. I don't remember much from the course, but the one concept that I do remember clearly came from the course textbook. In it, it was stated that one shouldn't refer to a person as their illness(e.g. "so and so is bipolar" or "so and so is schizophrenic"). This seems to me to be a very righteous statement. It is really disconcerting when I hear or see people refer to others by their mental illness as if that is what defines them.

"My bipolar friend." Why not, "My friend who has bipolar disorder"?
"My schizophrenic friend." Why not, "My friend who suffers from schizophrenia"?
"That person is ADHD." Why not, "That person has ADHD"?
"That person is anorexic." Why not, "That person is suffering from anorexia"?
"That person is psychotic." Why not, "That person is in a state of psychosis"?

Maybe this doesn't really matter, but it is really unsettling when I see it, nonetheless.

Would you, for instance, say:
"My cancer friend."
"My ALS friend."
"That Alzheimer's man."
"The dementia woman."
"The lupus girl."
"That person is COPD."

A person is not their disease. Why reduce them to such? Maybe I'm wrong. It just seems very strange to me.