Cancer occurs when a few invalid cells somehow don't get destroyed, as they should. They continue to replicate, but cannot do the job that they were supposed to do. Cancer is actually not deadly because the cells actively do bad things, it is just that they crowd out normal cells, and if the body function is vital, that is very bad.
"Plain folks" is a form of propaganda and a logical fallacy. A plain folks argument is one in which the speaker presents him or herself as an average Joe — a common person who can understand and empathize with a listener's concerns.
