They insist that you think positive, at a time when you are bald and nauseated and have a temperature of 104 and a major body part is missing. Preachers are usually well-meaning and sincerely concerned for your welfare, so they are hard to ignore. They are convinced that the one thing they promote is the thing that will cure your cancer, if you only do it correctly. This last part is the kicker - if it doesn't work, you must not be doing it right. The clueless make inane comments.
Cancer is really a blessing.
There are an infinite variety of idiotic remarks. When you have cancer you are liable to hear one or two that are amazingly thoughtless. If preachers are honestly concerned for your welfare, the clueless are primarily concerned about themselves. Those who deny their own sadness and grief do not want to hear about yours. The clueless want to believe that the world makes sense, that it is fair and just, that people get what they deserve.