The expression "demon possessed" seems to stir up a deep semantical resistance among many believers to the whole idea that believers can often benefit from deliverance, ie: getting set free from enemy oppression in one form or another or another. Can a believer be demonized as with being afflicted by such things as extreme depression, anxiety, fear, unforgiveness, severe pain in the body and/or a deeply blinding spirit of religion... and often be instantly set free through deliverance prayer? Of course!
Fixating on the term "demon possessed" rather than "demon afflicted" can thus create a stalemate that keeps the believer from seeking the help they need and from which they can truly benefit. Truly people's religious "certainties" which actually are quite false and debilitating (as was also the case with the pharisees) can often become their own worst enemy.
Blessings to all and may those in need crucify false certainties and seek the help they truly need :).