No, it's not a branch in the USA and yes, the constitution is its rules. These are rules under law. It gets funding from bodies which have their own rules and constitutions too. Some of these refuse or are not allowed (under the law) to fund organisations that engage in religeous or political activites. They could, quite rightly, cease funding and, worse, demand repayment, through the courts if neccessary, of any funding already awarded. I don't think that this constitutes a "silly" argument nor is it blowing it out of all proportion. These are simple facts but with serious implications.

Attempting to protect the organisation from getting into serious bother and wishing to support the organisation's aims and objectives in promoting "traditional", Irish music and culture to all people (regardless of their beliefs) is neither ignorant nor malicious.

The organisation is not a "closed shop" or there for the benefit of one demonination. This is clearly stated in its own constitution. Tokyo, for instance, has one of the largest, most thriving branches outside of Ireland. The majority of its members and supporters are, most likely, either Bhuddist and/or Shintoists and most welcome they are too. Religion should simply be left out of the organisation's activities. It plays no part under its own rules... and just look at the bother it causes :-)