A lot of people are saying stuff like Bud Light, and as someone who will not order a macrobrew even if I'm at a bar or restaurant with no craft beer whatsoever, I find that a pretty stupid and even pretentious thing to say.
And if Bud Light truly is the worst beer somebody has tried, it says much more about the person than it does about Bud Light. It says, "I am a person who hasn't tried very many different beers." Because, really, Bud Light tastes like fizzy water. It doesn't have a disgusting taste, it simply has no taste.
When you consider all the beers out there that aren't just bad, but can even have an intensity of flavor on par with an IIPA or barleywine, Bud Light just falls entirely off the radar. I mean truly offensive beers that you might even consider vomiting just to get that crap out of you, and the only thing stopping you is the realization that you'll have to taste it again on the way back up. Beer so vile that you would gladly drink your buddy's Bud Light because it's the closest thing around that might help you get the taste out of your mouth.
Sometimes it's the result of an infected or otherwise bad bottle or batch. Other times the beer is just genuinely that bad, whether through poor brewing/fermentation techniques, terrible recipe design, or some combination of factors.
Either way, truly disgusting beers, while not typical, aren't THAT rare, either. To have never encountered something worse than a tasteless Bud Light only implies that the person hasn't really tried many different beers at all.