True, a homosexual relationship is not "natural" in the sense it will not lead to procreation. However if you believe in a truly FREE society in which people are free to be who they want, and live how they want to, then you will stand against any fascist laws that suppress human rights and the right to a free existence---period. "Injustice anywhere is a threat to justice everywhere".
The function of Government isn't supposed to control or restrict people. It's supposed to serve the needs of the people, and that means all of us. Laws shouldn't be implemented against people based on our moral opinions.