We as Catholics can defend marriage without being discriminatory because, first of all, nothing in our definition is about “exclusion” in the pejorative sense. Rather, oddly enough, our definition of marriage acts as a definition. Definition is perhaps a form of exclusion, but to say that it’s a form of ‘humiliation’ is to introduce “convenient reasoning” to the argument. We delineate what marriage is, who may get married, and why they get married. We do so because it benefits the individual, the couple, the child, and their country. We do so because marriage for generations has been upheld for this purpose.
Amazing how that works. Once a thing is defined, that definitions excludes anything which doesn't fit. Once I have defined what a dog is, I have excluded all the cats, and once i have defined a fish, I have excluded whales. So it goes with marriage.