Oh Dear Me
I regret to inform the people who keep googling "Kant gay marriage" and "can gay marriage be justified by Kantian ethics?" that you've got some unfertile ground in Kant. That seminar gave me an excuse to buy The Metaphysics of Morals and things look pretty hopeless for gay marriage support in Kant.
This is not to say that Kantianism considered generally cannot be reconciled with gay marriage. But don't expect Kant to go to bat for homosexuals.
Sorry if I ruined anyone's day ;_;