What are some signs that a person might not react well to being told about a hygiene issue, and how can you approach it anyway?

Why do some people rush off airplanes when there's often a long wait at passport control anyway?
Why does a conversation that starts slowly always seem to end up somewhere more interesting than one that starts with energy?
Is it true that most atheists are not truly atheist but are just angry at God? What is your perspective on this belief?