This sentence comes from Lu Xun's article "Feuilly Should Go Slow". The metaphor "If you don't hit Reservoir Dogs, you will be bitten by a dog" means that you will not completely destroy the enemy, but you will be retaliated and hurt by the enemy. In metaphor, ontology and vehicle are divided into main and secondary parts, and vehicle is only a means to enhance visualization.
Metaphor is a commonly used rhetorical device. It is one of rhetoric figures to describe or explain things A with things B that are similar to things A..