There must never be social or political discrimination against any human being. There must be legal protection for same-sex couples to ensure appropriate justice in areas like property, inheritance, personal access, and so on.
But a same-sex union is not marriage, and can never be. Marriage is a vowed union of a man and a woman in a love from which human life can spring. A same-sex union is clearly not that, so this term marriage cannot be applied.
No other society in history has ever understood matter otherwise. The family as the basic unit of society is too precious for marriage and same-sex union to be equated.