The less offensive term of equal clarity and brevity is "British & Irish Isles". Believe when I say that the Manx natives have no trouble with this description as they are linked to the U.K. as a protected and supported territory, Republic of Ireland on the other hand is a sovereign nation with no link to the U.K.

Did you read the article on wiki about the basis for usage of the term? 
 
Completely flawed logic as it refers to ancient texts etc and precedent for calling them the British isles. Place names reflect current realities, thus we have Istanbul and not Constantinople. 
 
A better example would be the Aegean coast of Turkey and its islands. this whole area was once referred to as the Greek coast and all the islands were Greek islands. since the political landscape has changed and the Turkish state has jurisdiction, the only islands which are now "Greek islands" are those within the jurisdiction of Greece. if you were to rebut by saying that British refers to something more than a political term, but rather than an ethnic or geographical one, then the same argument (or even a better one can be made of Greek). the Greek world once referred to an area far greater than modern or ancient Greece (e.g. southern Italy, Sicily, turkey, Armenia etc) and many of the people residing in those parts of turkey which were formerly designated "Greek" are ethnically and linguistically Greek but live in the state of turkey, and therefore the islands and coast are Turkish.
 
Thus, you could not refer to the island of Ireland as British.