Undermines same-sex couples and single parent families as legitimate ways of raising children  As explained in the first proposition point, one of the primary functions of marriage is seen to be to raise children. Marriage is therefore seen as the best way to raise children. This undermines same-sex couples and single parent families raising children.  The existence of marriage is essentially saying that same-sex couples and single parents are less able of raising children than heterosexual couples. Marriage, therefore, can be seen to promote outdated ideals that our society no longer holds and, as such, is itself an outdated institution.