Would it be acceptable for a JW to join the Catholic Church, just to have access to some of the extensive services some of Catholic institutions provide? the answer is clearly NO.
So no excuse is really good enough in this case. If it is acceptable for the organization to join the UN, any JW can join any other religion as well.
And interestingly, just to prove that the organization indeed prostituted itself, and completely guilty as charged, can be revealed by doing a search in the WTLIB CD-ROM on the words "United Nations", and comparing the results between '92 and 2001 with any other similar period. it is striking how many 'positive' articles about the UN during the period 92-2001, and this almost completely stopped from 2002 onwards.