Here is a good site regarding dialects in the British Isles. As the author says, "There is a problem in identifying any dialect as the standard, since this implies that other dialects are inferior or wrong. In the case of spoken English, we have good evidence that such prejudice exists - so there is an exaggerated danger that, in referring to a standard, we will strengthen what is already a tyranny. It may help to note that Standard English, too, is a dialect - albeit one that is no longer found in any one region of Britain." How enlightening! We are teaching a dialect of English that no longer exists as a regional representation. Perhaps this is the ideal situation, and it would be if it were not for the social stratification and oppression that accompanies the domination of RP.
Now consider which dialect of English can boast the largest number of native speakers. Without a doubt it is American English. Likewise, in spite of the brink of recession that the US is on, America is the world's largest economy. Britain as a whole comes somewhere near 5th. Consider that RP is really tied to England and then try to place England alone on the list of economies and you get the picture.
The opposing argument here in Poland goes something like this. England is closer than the U.S. and visas to work in England are no longer required. What they really mean is that visas to work in Ireland are no longer required, since far more Poles land there than in England. So RP does not really blend with the Irish Catholics' politics and ultimately places you on the outside even more than simply being a foreigner. Whereas, speaking the American dialect of English in Ireland is not nearly as offensive.