… since you are the ones trying to impose your beliefs on those who do not share them,…
There is no objective evidence that their relationship… hurts anyone.
Let me dispense with this “objective evidence” criterion once and for all.
There are two questions we might ask about this issue. One question is whether same-sex marriage should be recognized by our society through our government. The other question is whether it is morally acceptable for one side (i.e. the anti-gay marriage group) to impose their will on the rest of society, including those who do not share their belief, just by force of majority vote. In this forum it sometimes happens that these two questions are treated as the same question. But there is an important difference between these two questions that I hope to explain. When these two questions are conflated, in an effort to answer the first question, someone may actually address the second question with an argument that goes like this:
You must show objective evidence that gay marriage is harming anyone, or else it is not fair that you should impose your will on those who do not share your belief.
The implication inherent in this argument is that the anti-gay marriage group cannot morally justify imposing their will on the rest of society without presenting what everyone agrees is objective evidence to back up their belief. I claim that the “objective evidence” criterion only applies when trying to convince someone of your belief. It does not apply to the question of the majority imposing its will on a minority.
To prove that point I will pick an analogous issue – like the selection of a national leader such as the President. Just like the gay marriage debate, there are people on both sides who strongly believe in their choice. Just like the gay marriage debate, when trying to convince someone of the rightness of your choice, you normally employ what you think is objective evidence. This evidence may not appear objective or even factually correct by the other side. But if they do accept it as objective evidence, they may change their minds and switch to your side. And just like the gay marriage debate, when a choice is made that some people strongly disagree with, those people are going to feel (and maybe will actually be) greatly harmed and inconvenienced by that choice. But here is the key thing. At the end of the day, after everyone has tried their best to convince the other side of the rightness of their choice, the will of the majority
does get imposed on the rest of the people, including those
who did not share the belief in the rightness of that choice. But no one seriously thinks the majority is necessarily unfair to the minority when electing a President just because they were unable to present convincing objective evidence to those who did not agree with them. In other words, the criterion of “objective evidence” is reasonable when trying to convince someone of your view, but that criterion is not reasonable when it comes to implementation of the decision once it is made by majority vote. This is the key difference between the first and second questions mentioned above.
This same consideration can be applied to any number of public policy questions too. You can expect to have to produce objective evidence when trying to convince someone of your view. But you cannot expect that acceptable objective evidence morally must be provided in order to implement a decision made by the society.
So when applied to the issue of gay marriage, this says that when I try to convince you that gay marriage is bad, you might expect that I give you objective evidence of that view. But if I cannot convince you after trying my best, then just as in electing a President, or deciding on minimum wage laws, or trade policy, the majority does morally impose its will on the minority. No one would call that intrinsically unfair in those other areas. And it is not unfair in the gay marriage question either. If you are not convinced, then too bad. That is the way it is when public policy questions of all sorts are decided. Why should it be any different with gay marriage?