Well it looks like this has been an issue for a couple of years now according to the article on 365gay.com
The organization that organizes and puts on the nationals largest St. Patty's day parade in New York is extremely Catholic and has refused to allow gay Irish groups to join in the parade. "For 18 years the Ancient Order of Hibernians which organizes the parade has barred Irish gay groups from marching. "
Some of the LGBT community find this completely disrespectful and did not join in on the festivities. "The city’s highest ranking gay politician, City Council Speaker Christine Quinn, boycotted the parade again this year. As she did before last year’s parade, Quinn attempted to set up a meeting between the Hibernians and gay representatives and again this year the conservative Catholic men’s group ignored the invitation.The Hibernians claim the parade is a private, religious procession in order to to justify keeping LGBT groups out."
So are religious processions normally followed by Irish car-bombs and green beers till you can't see straight? Because if that is the case then sign me up!