I do not remember which priest said it on a TV interview - after the Vatican meeting of the American Cardinals - but it made sense to me -
A homosexual is a man who defines himself by his sexual preference above all other facets of his life.It is this focus on his sexuality that would make him unsuitable. Heterosexuals do not put 'heterosexual' first on their identity list.
A candidate for the priesthood would not have to 'prove' that he is attracted to women. He would just be a 'man' who wanted to serve God in His ministry.
I think that is the distinction that Father Neuhaus made on Sunday: A "gay" is a person whose whole personality is involved in his homosexual life. We CAN distinguish him from the guys of uncertain sexuality who has experimented but can take it or leave it.