Yes, there are many topics similar to this subject, but I figured I would post this here for those that wish to contribute their ideas and thoughts. And when I say "respond" I mean that the conversation comes my way. Not that I go hunting for this person.
I might be asking for the impossible, but here is what I wish to convey:
I don’t want to appear like I despise the person
I don’t want to explicitly or implicitly condone their lifestyle. I don’t want to be deceptive and dodge.
I want to be clear about my position (the official Catholic position), which is that I believe marriage is objectively between a man and a woman, that it is lifelong, that it means putting your spouse and children first.