Marriage is a legal and social institution with a biological foundation, which helps to bind a male to his mate for stability and for the children they might have.
Not all marriages produce children but typically they do, and hence the need for this institution.
Obviously, homosexual relationships cannot naturally produce children, so society has no formal interest in such private affairs.
Some want to claim the right to separate sex as recreation from baby-making, and by doing so deny a child's prior birthright to its natural mother and father.
Making children artificially in a same-sex relationship is unnatural and damaging to them.
The claims from personal "experience" and "tests", both here and overseas, that there are no apparent differences between the behaviour of children raised either way are shallow and biased.
It is a trivial argument to use behaviour checklist against the basic principles of natural law confirmed by the extensive multi-dimensional, long-term, controlled testing of these surrogate children.
Thorough tests show the deeper damage and long-range effects on children deprived of biological identity and the emotional security of the bonding touch and feeding of a mother, and the firm modelling of a father to adulthood.
People in same-sex relationships only want recognition of their unnatural satisfactions while they ignore the important natural links in the chain of generations.
Children deprived of their rights may very well complain of a new "stolen generation" in years to come.