Love and commitment? Physical attraction?
Bah. Those are just luxuries we've been indulging ourselves with lately. They certainly aren't the norm when you look back on what sex has meant to humanity for most of our history.
Even today, the debate isn't really over biology. If it was, we'd just note it was a biological reality and move on, or else we'd dwell on the dispassionate biological and medical implications of it. We don't, though. What are the objections to homosexuality usually based on? They're trying to corrupt / seduce children. It's bad for society. It's a sign of moral decay. It's against the word of God. We shouldn't redefine marriage for gay people. They're "pushing their agenda" on us. Gay people want to force us to give them "special rights"... etc, etc, etc.
All of those are socially based objections. Even today, the debate over sex isn't about sex. It isn't about the biology of the thing; it's about social posturing and positioning, power and control, of defining people's social status. That we're doing it over sex is incidental. Thirty years ago, it was about gender equality. Fifty years ago, it was over skin color. Seventy years ago, it was about what country your ancestors came from. Two hundred, it was over religion.
Today, it's a status struggle over sex, but the nature of the current debate, along with the plasticity of sexual morals, expectations, and expression over the course of our history is a pretty clear indication to me that social conditioning plays a very important role in how we shape and restrict our prurient thoughts, and how we channel our sexual urges.