Take a look at this thread -- Marriage and "De Facto" Unions (Cohabitation and Homosexual Marriage).
It's a perfectly objective discourse on the essential differences between marriage and de facto unions. It defends marriage absolutely, recognizes precisely the differences which set marriage apart and excoriates de facto unions without damning to hell the participants in same.
If you can improve somehow on the argument (or prove even one point objectively wrong) by virtue of your having been a homosexual, shacked up or married ... please let me know. I'm very interested.
The true beauty -- for me, anyway -- of the priest's counsel is that he is limited, or should by all rights limit himself, to what is Enduring and Universally true about marriage, sex, love, commitment, children, family, etc.
It is EXACTLY when some participant colored by experience or pycholo-psychiatrist colored by their Method seek to impose always Their Own Views that one runs aground. Lessons learned or imparted in the strictly personal or particular do not end up of much enduring value.