That is a pretty sweeping generalization to make. I've been sick with ME/CFS for several years now and I've never come across another patient dismissing psychological illness as not debilitating. Instead, many that I know have premorbid or comorbid psychological illness and know firsthand how debilitating psychological illness is.

If a person with OCD was told that their illness was due to poor lifestyle choices and that they could be cured of their OCD if they just stop believing they have OCD and that they just need to get to sleep on time and get a bit of exercise, they would probably not appreciate that. This is how people with ME/CFS are treated by many health professionals and medical researchers. There is a large and influential group of psychiatrists that posit that the disease is caused by nothing more than the belief that you have a disease. This is why there is seemingly an intense backlash against psychiatry and a frantic hunt for biomedical proof in ME/CFS.