I previously discussed the Washington Redskins' trademark. It is being challenged by a group of Native Americans who find the mark disparaging, offensive and/or scandalous. More than a decade ago, the mark's federal registration was challenged on the same grounds. The reasoning was that the mark is entitled to registration, basically because more people associate the mark with the football team than with its offensive meaning.
This is a good background article to the Trademark Trial and Appeal Board, the group charged with making such decisions. The TTAB oversees petitions opposing and to cancel a trademark, along with interference and concurrent use proceedings. The TTAB does not decide whether a mark can be used or is being infringed; it only determines whether a certain mark is entitled to federal registration.