I don't think it being offensive in some way is nearly the biggest issue. The theme is ubiquitous both as a theme park motif but also there are museums, ghost towns and still existing towns that have not changed much. It really is anachronistic within the MK. And it impedes growth in the park.
Disneyland is different because it was built at the height of western tv and movies. But most importantly, was something Walt Disney cared about and directed the design. So it is iconic there. At the MK, it is just a poor recreation. IMO.
Hold on, I got to get my Scrabble dictionary.
I disagree that Frontierland should be replaced. It's one of my favorite lands in all of Disney World. I usually go left whenever I enter Magic Kingdom. If anything they should just add to it (Western River), not take away.