I've done a bit a digging, with a pointer from Frank McNally himself, and found that in 1999 he published an "Essential Guide for the first time traveller to Ireland" below is an extract of the article which can be found in full at:-

http://www.irishcultureandcustoms.com/atravel/travelguide.htlm

Traditional Music
Many visitors to Ireland make the mistake of thinking of traditional music as mere entertainment. In some parts of Ireland this may even be an accurate impression. However, in certain fundamentalist strongholds such as Co. Clare, traditional music is founded in a strict belief system which has been handed on from generation to generation. This is overseen by bearded holy men, sometimes called "Mullahs", who ensure that the music is played in accordance with laws laid down in the 4th Century. Under this system,"bodhran players" are required to cover their faces in public. Other transgressions, such as attempting to play guitar in a traditional session, are punishable by the loss of one or both hands. A blind eye may be turned however to the misbehavior of foreigners, but it's best not to push it.

I recommend you read the rest of the article it's very tongue in cheek and quite amusing

I think the best we can do is ignore the bile that has occasionally surfaced in some posts and trust that the hospitality we have received in all the other places we have visited can be found on this trip, if not we will have to put it down to experience and spend our money somewhere else next time. Having said that, the negative comments have not, to my knowledge, come from people who own businesses that rely on tourism but from individuals who may or may not have a vested interest in tourism.

Incidentally Frank wished us well for our forthcoming trip.

Cheers

Raggytash