I would not waste my time trying to convince someone unless they asked for advice. And giving unsolicited advice is an extremely thankless task. You know that delusions are a temporary part of the human worldview, and if you try to convince a person, they simply may not believe your words. A person must see for themselves that they are wrong in practice. I always say that practice has the highest degree of reliability. Besides, why waste time trying to convince someone? As one psychologist said, criticize for money, and only praise for free.