Not the worst commercial beer, but definitely a not-so-great interaction with a brewery (I won't name them unless someone really wants to know who).
It's a brewery out of Austin that mainly makes so-so beers. I tried their brown ale over the weekend while in Galveston and found it to be really harshly bitter. Like they had used hard water or the wrong kind of bittering hop. I was probably a little harsh with the rating on Untappd (gave it a 2.5*) and left a little comment saying that I thought it was too bitter. The next day I get a comment from them saying "The style is 'Texas Brown Ale', here is the history" (article with history of American Brown Ales linked).
I read the article and learned about the story that the American/Texas brown ale has its origins in homebrewing (apparently in Texas, but then commercially in California). Interesting read. But the thing is, I know about the style. I wasn't comparing it to an English Brown standard. Maybe my comment came off a glib and rude, but holy **** man, that's some bad PR making comments as rude as that to customers.
I have given a 0.5 star rating to a small brewery because it was just a nasty beer, then given another one of theirs a 4. I commented that it was the best by far from them and they responded saying "glad you found one you enjoyed, please keep drinking!". That to me sounded like a good PR work. Don't try to respond to negative comments sounding like you are going to lecture a consumer.
I also kind of had a bad taste in my mouth about this brewery ahead of time. Last year (or maybe 2 years ago) I went to a beer festival here in Houston. I recognized the head brewer by name behind their table. When I asked "hey, you're the owner and head brewer right?" I got a haughty "yea" and nothing else. I was excited and wanted to try more of their beers, but after that I felt like he had no interest in selling me anything or getting me interested. This guy has been part of the homebrew community for years, so I was excited to meet him and figured with his history he'd be great at it. Now I just have no interest in their beers anymore.
*My rating scale generally goes like this:
0-1: not worth drinking
1-2: flawed beer, would drink if it is the only thing available
2-3: has issues, wouldn't buy for a party or hanging out
3-4: no flaws, would buy as a drinking beer
4-4.5: technically no issues, but not my favorites
4.5-5: my favorites
I also try to only judge on style, not on what I like. In other words, I won't give every cream ale a rating less than 3 just because I am not a fan of the style.