Ireland Transit Visa when flying from IND - Abu Dhabi - Dublin - US

My parents are Indian Citizens. They hold a valid B2 Tourist Visa to USA. I'm planning to book a flight with Hyderabad (India) - Abu Dhabi (UAE) - Dublin (Ireland) - USA. The leg from Hyderabad to Dublin is operated by Etihad and I know there is no problem hopping at Abu Dhabi. The leg from Dublin to US is operated by Aer Lingus. I called Aer Lingus customer care agent told me a transit visa is required to land in Dublin. She did not care to ask for the citizenship of traveller or about the USA visa. I went through Irish immigration website - (http://www.inis.gov.ie/en/INIS/Pages/Transit%20Visas), India is not in list of countries that require transit visa. I'm now confused. Can some one confirm if they traveled with the same itinerary recently

Update: I called Aer Lingus again. Another agent told as long as I don't exit the airport, a transit visa is not required. I think these people don't really understand trouble we go through when boarding is denied. I put this question because I read a person was denied boarding earlier - Do I need a UK or Ireland transit visa when flying from the US to a Schengen country?. His case mentions about denied because of different day. But I see his transit time is 12 hours only.