Heterosexual couples are allowed to marry because until recently, there was no means of knowing whether they were sterile or not.Insults reveal your argument has no merit.
Sterile people as well as those with no ability to have sex are recognized as retaining the fundamental right of marriage. Because marriage is a fundamental right of all persons, facts of sexual ability and procreation ability are irrelevant, and insufficient to deny this right.
Yet same sex couples are raising children, and denial of the legal protections of marriage to their family, only harms them, while providing no benefit to opposite sex parent families, or couples who choose not to reproduce, or are unable.
Your personal prejudice is fine for your own life, but it has no place in the law.
A far cry from a duplicate gendered couples who are totally barren.
Marriage defines a distinct relationship. Ss couples cannot equate.