The first time, you might wonder if you imagined it as it happened so quickly and you've never seen the guy before. So you let it slide.
But the second time, you realize it's the same guy and that you obviously did not imagine the first incident. So you report his Neanderthal ass to the management - who, it turns out, takes this sort of thing very seriously. The assistant manager assures you that such conduct is "completely unacceptable and can lead to membership termination."
Stay tuned for further developments.