Obviously their genders are different. One kind of couple can reproduce. The other can't. The differences are more significant than the differences between a monogamous marriage and a polygamous marriage.
I understand your position....but there are holes in it.
Can two sterile people marry? One sterile and one fertile?
Marriage is not about sex and reproduction. That is biology.
Marriage is about love.
There has never been any impediment to Steve and Bruce walking together to a beach and at sunset pledging their eternal love to each other and marrying each other and then living together and celebrating their love. That's a marriage about love.
There is absolutely NO BENEFIT to society when two people pledge their love to each other. Normal people or homosexuals. None.
The only benefit to society is when children are born. Society, as an entity onto itself, needs to be self-sustaining. Society doesn't give a flying **** about how happy people are, society cares about continuing on.
Marriage is about raising a family. That existed long before the notion of love being the basis upon which two people join together. Even today we see arranged marriages. There's no love when these marriages begin so by your definition that husband and wife who are trying to have kids and begin a family are not really married.
You do not need to be part of the gay lifestyle to respect the fact that two human beings love each other so much, they are willing to be made fun of, excluded, pushed aside....all in an effort to express and enjoy their devotion for each other.
Have a heart man. It has absolutely no affect on you whatsoever.
Down the block from my home lies a widower and his divorced daughter and her two sons also live there. I've known them for about 5 years and while they're not close friends I can't recall every seeing either of them with what looked like same-age dates. To me it appears that they've settled into a comfortable life raising her sons, his grandsons. She's the "wife" and he's the "husband."
To my mind they deserve to be married more than do Steve an Bruce and the 6 partners they bring into their marital bed every year,.
Why can't a father marry his daughter? Remember, you're claiming that procreation is not a necessary component of marriage.