Peter Benchley

A human being is still more likely to die of a bee sting, snake bite or, Lord knows, automobile accident than by shark attack. We do not execute the perpretrators of death by car. We should not butcher an animal for an inadvertent homicide.

The historical novelist has to consider what has actually happened, while the SF writer is dealing in possibilities, but they are both in the business of imagining a world unlike our own and yet connected to it.