There are a number of things that I just don't understand:
1) Musical theater. I can enjoy music, and I can enjoy a play, but somehow these just don't go together. Partly because the realism of the play gets ruined when everyone breaks into song--folks, this just does not happen in real life! No matter how drunk you get you're just not going to start a big number with a backing orchestra with all your friends in tune. Doesn't happen! But also, the songs just aren't very good.
2) Ice cream cake. See 1), above. Ice cream--great! Cake--delicious! But put them together and it's all "eek!" because you bite into the cake and your teeth get cold. Forget it!
3) The concept of not enjoying a joke because it's offensive. The offensiveness is often what makes the joke funny--the taboo of laughing at something "wrong". Usually, the joke actually pokes fun at what is itself offensive (racism, irreverance toward religion, raunchy foul sex). Now, if the joke is just not funny, THAT'S inexcusable. But funny isn't trumped by offensive.
4) Orange tans. I get why a slight cream or mocha color on your skin is attractive--to the extent it's a natural look. But that glowing orange look? Who ever saw the Oompa Loompas on "Willy Wonka" and said "now, I gotta get me some of that!"?
5) Hair extensions. No explanation necessary.
6) Anything that "looked good" in the '80s. Jeans pulled way too high, bright white sneakers with everything, giant shoulder pads on women--how does a culture get together and say "hey, looking like crap will be the new hot!"?
7) Rock songs with saxaphone or synthesizer. People, this never improves a song! I know your buddy plays a mad sax and doesn't like the guys in the local jazz band because they're jerks, but that doesnt' mean he should get to join the rock band!
8) Super thick french fries. If I wanted a potato, I'd have ordered a potato!