Instant karma, just how we like it. So there's this dude behind the bar, serving up drinks for a massive party of around 400 people. And if that ain't stressful enough, in walks the grumpy host who's been acting like a total snob from the moment he strutted in. He's all about having things his way, and he's got zero faith in our poor bartender's ability to do his literal job. Our bartender is seething on the inside, but the guy's paying the bills, so he keeps it cool. To make matters worse, the…