The person you argue against could counter by saying that at least heterosexuals have the opportunity, theoretically, to find somebody willing to consent, then get legally married, whereas the homosexual does not have that full opportunity, as the law does not recognize same-sex “marriages”. It’s an interesting observation that may leave a few stumped, but I wouldn’t expect this to be an ace in the hole. I think we just need to get straight down to it and remind people that God designed the intrinsic nature of heterosexual marriages as being procreative. Copying someone’s post from a different thread on another website, I will say, “Whether or not there is infertility due to defect or age, the conjugal act is ordered toward procreation. It is, of its very nature, different from every other sexual pairing.” The debate, dominated by secularists, will of course disregard any such religious ideas, but we should not seek to water down our arguments to anything less; ultimately, this is about standing up for the truth, regardless of whether or not society as a whole decides to accept it or not. That’s not to discourage effective arguing and bringing up other good points, but it all ultimately boils down to an issue of the intended design of human sexuality.
But the opportunity does not present itself with everyone. To be truly a right, it has to be there for the taking. Voting is only taken away when a person commits a felony. Marriage is entirely dependent on another person...you cannot marry yourself...Mick Jagger tried with Bianca and failed.