Thanks for bringing up this important topic. I do not know of any other documented cases of transmission through kissing or receiving oral sex than the infamous case to which you refer. I would agree with you that people should try to forget about being infected if they are at very low risk for infection. That is much easier said than done.
People worry about many different things.
Some worry about HIV, others worry about their physical appearance, and some worry about flying in an airplane. The feelings and symptoms associated with anxiety tend to be quite similar. Chronic anxiety can be a truly awful experience for a person, and some suffer needlessly from it. It seems pejorative. Telling somebody to forget about it dismisses the authenticity of their emotions.