First and foremost, the use of the word "conquered" in reference to an attraction specifically built to promote world peace and brotherhood for the 1964 World's Fair in New York is disrespectful. Think about any conquering of a country in history or present time and it brings to mind murder, war, sickness, rape, and other atrocities. There is absolutely no need to associate that word with a concept that was completely counter to any of those ideas. With all the modifications it's a small world has endured over the years, the central theme of forgetting our differences and embracing our similarities has been chiseled away little by little. The addition of Disney characters turned the ride into an Easter egg hunt instead of a relatable message. I stand by the argument that it's a distraction since I can't ride it anymore without noticing my fellow passengers become absorbed in finding each character instead of taking in the big picture. The modification, including an "American room" at the end, dominated with white settlers and cowboys and sprinkled with Native Americans here and there, takes away from our global happiness and reminds us before we exit that we are, in fact, different. Now this shirt reads as another reminder that this attraction doesn't speak to its general audiences as it once did.
This leads me into my second point, that I believe Disney should be extremely supportive of the lasting legacy Walt has left that continue to remain in the parks. To imply that this historical ex-World's Fair exhibit is something that needs to be "conquered," or even survived to the extent that it invites being mocked it is just distasteful to me. And I do understand that the song can be annoying to modern-day audiences without historical insight. But it is also a song written by legendary songwriters Richard and Robert Sherman, one of which is still alive and doesn't need to have his talent insulted outwardly by Disney.
The latter point is an opinion, of course, but I stand by my statement that using the word "conquered" is offensive in this instance. I, perhaps naively, only wish those involved in Disney merchandise would think a little bit deeper about the messages some of their items put off, whether intentional or not, before trying to turn a dollar from them. It's just unnecessary.