I'm going to regrettably enter this hell storm.
There seems to be an erroneous connection between biblical morality and the "right" to choose. Which first, there is a difference between the "right" to choose, and the "ability" to choose. To say that people have the ability to choose is repetitive and distracting. Of course they do. It has no relation to statutes, or policies. If someone chooses to do something, it's on them. If they murder someone, yes it's against the law, but does that law prevent them from doing it? The important part of law, is sentence. It isn't the law that makes an order, it's fear of the consequences. When people choose to not fear those consequences, the law is as valid as any other ink on paper. So to say, "I won't vote against it, because everyone has the right to choose.", doesn't make any sense, as "right" declares a statutory endorsement. If no law exists supporting, then there are no "rights". Choice has no relation to law. Law only affects people psychologically, not morally.
So hopefully this washes away the thought that supporting a law to oppose Gay marriage, prevents them from having the ability to choose. Especially due to current law not having any sentence attributed to the breaking of the law. So YES, people are going to do, what they want to do. Regardless of how another person raises a stink about it.
This all being said, we are to love all of God's children. Apathy is not love, in fact it's closer to what eternity without God would be like; emptiness. "That kid just ran out into the middle of the street to play around, and a car hit them. It was their choice." It was also the choice of the observer to do nothing. The congruency of these choices resulted in the consequence. To be dismissive of someone else's choice, and then consider it support, is simply apathy. When we choose to just not care, we aren't sharing the love of Christ. Can we choose for people? Well, of course not. What we can do is be plain about where we stand. With others, let them observe Christ in us through our living testimony (not how loud we are). When they DO ask us what we think, we don't say "Do whatever you want to do, you're just going to do what you choose anyway." They know this, it doesn't help them. Say instead "These acts are sinful, and a perversion to the natural order set in place. Even so, coming to Christ washes away these and all sins, and enables you so you will not be slave to them anymore. When you observe me do what is good, it is not of my will that I do them. Instead, it is my surrender to the will of God. Only through the spirit of Christ, that now dwells in me, am I enabled."
Be plain with the truth. We do need to add salt to our words and choose them wisely, but we do not change the plainness of truth. As Christians we are not of this world, but we are in it. We are also called to love all of those in it. We do not dismiss the ones we love as trivial. When we see sin in the world it shouldn't surprise us, but it should still affect us.
To say that we don't want to force someone into something, is assuming we have the power to force someone else in the first place. Only God can change a man's heart. No law, be it written by man or God can. Only the very spirit of Christ. So the foolishness is revealed when we don't do (which includes voting) according to what God has revealed for us. God's will is going to happen one way or another. The way we vote won't change that. However, those ballots are asking US how WE feel on issues individually. When we think, "I'll just vote how everyone else will vote, because I don't want to force my opinion down their throats.", we're actually being arrogant enough to suppose that what WE say, others will do. Just treat it like someone asking a question. Answer it plainly and truthfully. You don't even need to salt your words because thankfully, paper doesn't have emotions. Politics are a thing of this world, we shouldn't bag it together with the realm of God. No principality of this world has the power to supersede his will.
The main guts of this argument, like any argument, is the assumption that what we say will change someone. Not gunna happen. What will happen, is everyone's going to be impassioned by the affront to their own pride to the point where they will take offense to anything that one person says, because they are now an enemy. Arguing against God's will is foolishness. So why humor a fool by giving them more opportunity to be foolish? Nothing comes from egging people on, but more of these 10 page plus threads that don't help anyone. I could guilt trip here, but I won't

. I've said this much, and that's all I'm going to say. If I was unclear at any point, just ask me what I meant. I'll be happy to answer.