The latest entry, with some insight.
Science fiction is about fiction and space opera is about opera. If people want to read about science or space, there are plenty of non-fiction books, magazines and journals to choose from. If people want to delve into ordinary human drama, they just have to live ordinary lives or pick up lit fic. The science in science fiction makes the fiction fun, and the space in space opera is the setting for the opera.
Science fiction is not about dragging readers through muck and demanding they derive pleasure from it. Science fiction turns their eyes to the stars, and space opera takes them there. Space opera is about opera: the glory, the terror, the joy, the horror, the sorrow and the wonder that awaits the intrepid starman who dares to brave the infinite expanse.
Go read the thing already.