For me, to make fiction realistic is to have normal people in the story and have something strange come out of the blue. For example, there are researcher that study UFOs, so maybe have a conflict that has something to do with UFOs. Hope that helps!!!
The phrase, a decent respect for the opinions of mankind, was intended to convey a respect for what mankind thinks. Opinions are biases indulged by mankind inside their thought-matrices. Mankind is the species known as Homo Sapiens Sapiens.
"How to prepare for a job interview" or "Why interviews are important" I believe