It's the kind of thing that, were it to happen in real life, would be appalling on multiple levels: dude talks shit while walking by, another person pulls out a weapon. But because it happens in GTA V, it becomes comedy.
It helps that the timing in this quick, 9-second clip by YouTuber something i dunno is just about perfect. You can almost see the AI behavior scripts shuffling inside the NPC's skull, making for a bit of improvised comedy. But it also highlights the weird paradox at the core of Grand Theft Auto's DNA, where everything happens in an extreme, outrageously skewed version of the real world. It's the similarity to reality that draws people in and the chance to trample all sorts of social niceties that keeps them there.