Of course, some True Christians would tell you that no, there is no way that True Christians would support marriage equality. Sure, they wouldn't go around picketing funerals like Westboro Baptist, 'cause that's too over-the-top, but God clearly set out rules for what He wanted marriage to be, and Adam marrying Steve just ain't what's happening.
Whatever you do, don't ask the extremists in Westboro what a True Christian is because they'll go and tell you that it's THEM! Can you believe that? Just because they can point to various Bible verses to support their cause, they somehow think that trumps the more equality-minded Christians who can also point to Bible verses to support their cause. Clearly, The Bible is unambiguous as to this issue, just like it was with slavery. After all, it was Christians who led the abolition movement, and there was absolutely NOTHING that slave owners could have pointed to to support their cause. To say that they could would be as ridiculous as saying that The Bible says it's okay to beat your slave, so long as you don't beat him to death (Exodus 21:20).
The thing is, if you want to know what a True Christian believes, you turn to the Book of Who's a True Christian in The Bible. (Muslims, check out the Surah of Who's a True Muslim in The Koran so you know whether it's okay to blow up infidels or not.) It clearly lays out what you should and shouldn't believe. This is why we only have one denomination of Christianity, known as the True Christians.
Okay, just in case you're about to explode from all the sarcasm, my point is this: lots of Christians believe a lot of different things, and as far as I can tell, there's no real way to tell who's believing it the "right" way. The differences aren't what I'd call insignificant either. But each side will point to the verses in The Bible that helps their cause while either completely ignoring the verses that argue against it. (Or more infuriating - telling you that it actually means the opposite of what it says.)
Meanwhile, the simplest explanation doesn't seem to occur to any of them, and that is that The Bible doesn't even have a consistent message. Is there good stuff? Absolutely. Is there screwed up stuff? Yes. Is there stuff that contradicts other stuff? Yes, and that's the problem. Even Jesus, the guy that some wishy-washy freethinkers will praise, insists that all the Old Testament rules count. He also says that you have to hate your family if you want to follow him. Remember, he came with a sword, or so he says, but nobody likes to quote him on that (except maybe the True Christians, depending on who you think that is). Yeah, there's a lot of stuff that Jesus says that I like, but at least I admit that I pick and choose the bits that suit me.
You know what you never get from atheists? You never get the "He's not a True Atheist" line. All one has to do to be a True Atheist is not believe in any gods. From there, he can be anything else he wants. Of course, there are times when we have to point out that Hitler wasn't an atheist, but that's not because he was evil but because he spoke of things like divine providence - something that doesn't make a whole lot of sense for an atheist to believe. Also, we'll point out that the Communistic regimes that led to the deaths of billions of people weren't about atheism, even though much of it was led by self-proclaimed atheists. They did what they did in the name of nationalism, industrialism, worship of the state, etc. There's nothing about being an atheist that leads one to support those ideas. In other words, that would be like blaming Christianity for the actions of BTK, a notorious serial killer. Turns out that he was a regular church-goer. However, he didn't do what he did in the name of Christianity. So, his being Christian is as relevant to his crimes as Stalin's supposed atheism (one of his biographers apparently insists that he actually was a main of faith - whatever, I'll just give it to you that he was an atheist for the sake of argument) was to his.
So, who are the True Christians? I don't know, and I don't think that anybody else does either. All I know is, it's an easy way for some of them to disassociate themselves from the ones they don't like. Meanwhile, I'm stuck with all kinds of murderous atheists who are as True Atheists as I am, but that's just because the definition is such a clear one. Personally, I would be fine if everybody agreed that a True Christian was one who believed in the resurrection of Jesus Christ. From there. I think that umbrella would be a bit too wide for the comfort of many people though.
Oh - and in case you're wondering what Scotsmen have to do with this, I'm referring to the "No True Scotsman" fallacy.