The reason for this is that when I directly challenge something you think to be true, it is no longer the belief that is under assault, it is you – and your instinct for self-preservation will come to your defense. At this point, even an idea you may not have fully believed becomes rooted and grounded in your very being, and you become almost incapable of giving it up. Doing so would be admitting defeat, something we find so distasteful.
The only method to effectively influence others is to recognize the inner makeup of the human, and to then gingerly bring people around to the correct understanding, allowing their sense of self to remain untouched.