Most of the time when bystanders interfere with field reports, the reporter will handle it calmly, either ignoring the interloper or quickly cutting back to the studio. Fortunately for us, this is not the case here. This is obviously the culmination of an extended period of antagonism, which we don't see but was probably also hilarious. It seems like, "we can't get this guy to leave, but fuck it, LET'S DO IT LIVE!" But then the reporter loses his shit. It's priceless.
Two additional things worth appreciating:
1. The drunken fool appears to be alone. There's nobody egging him on, he's just such an asshole that he will ruin stuff solely for his own enjoyment.
2. The anchors' faces.
What happens in Vegas, AMIRITE? HUH? HUH?