In the past, I've debated this point with them, trying to get them to explain to me how my marriage affects them. They always have plenty of reasons why they think it affects them, but this approach never gets anywhere, since the whole reason they're invested in this is that they don't understand boundaries in the first place.
I've also tried debating theology with them, explaining that the scripture doesn't actually say what they think it does, or in many cases, demonstrating to them that they aren't even familiar with it. Similarly, this doesn't get anywhere, because the basis of their beliefs is that someone told them what to believe, usually in the context of a family and/or religious community in which dissent is not permitted.
So I think I'm going to make this a lot simpler. Next time someone tells me that "it's wrong," either because of their interpretation of scripture or just their personal beliefs, I'm going to emphasize that same-sex relationships are wrong for them. When they insist that this means it's wrong for everyone, I'm going to ask them if they keep kosher.* When they say that of course they don't, because that isn't their belief, I can draw the obvious analogy.
If I believe the moral thing to do is to keep kosher, shouldn't I try to get a law passed, so my children aren't exposed to people who are so immoral as to not keep kosher? Besides, there's no language in the state constitution specifying that the right to vote/marry/own property is extended to people who don't keep kosher, so why do activist judges keep ruling that these immoral people have special rights like voting? And hey, if you want people to just leave you alone, then why not just do the obvious thing and start keeping kosher? Wait, what? Because you're not Jewish? Well, I'm not a fundamentalist Christian, so that's why I don't think my existence is immoral. So how about, I'll keep kosher, you refrain from same-sex relations, and we'll both be practicing our belief systems.
*I realize there are also Jews whose personal views or denomination views oppose same-sex marriage and relationships, but practicing Jews do not typically attempt to have their beliefs written into secular law. Also, no, this is not an attack on Christians, but rather on Christians who have no boundaries. If you feel you're being attacked by this, then, well...