Err ... because of adherence to supernatural claims. Hence you have demonstrated that your assertion that there are no examples where introduction of the supernatural into psychology has been detrimental. Clearly there are many examples - and while some none supernatural interventions have have been misguided they would have been based on some semblance of evidence, even if that evidence proved to be wrong. Appealing to the supernatural is evidence-less.
I would disagree that the psychological contributions of the religious have been all, mostly or even half bad and many practitioners would acknowledge the therapeutic value of chaplains.
Religion provides psychological support when the secular authorities can't or won't provide it and it is undeniable that the practitioners of medical science provide, in many places, on a commercial basis.
