They are able to be healed, they just almost always aren't because they are either unwilling, or they don't know how. Sexual perversion is like any other perversive habit: we continue doing it because it fulfills some need in us. Now, the need itself might be perversive, I admit, and indeed if this need couldn't be changed (as some psychologists would argue, and agree with you) then I would have to agree that they should be locked away. However, people CAN change. Even if you discount all the conversions from scoundrels to saints in the church hagiographical literature as nothing but myth, still, I think you have to admit that there is something that can change people. Otherwise, why are you a Christian? I mean, you're a dirtbag... we all are. Some are better at hiding it than others, but compared to God's morality (whatever that might be), we'd all have to seem nearly irrevocably evil.
Think of it this way, if we were all placed on a continuum, God might be placed (just for the sake of demonstrating the point) about 2 million light years to the right of center. All men would be a hundred miles to the left of center (center here being, let's say, the highest morality a created being can attain). Now, Hitler or Stalin might be 200 miles to the left, while TomS might be 95 miles, and thus from a human perspective Hitler and Stalin are greatly more evil than TomS. However, from God's perspective, the difference between Hitler and Stalin seems less acute; Hitler and Stalin had power, TomS does not; Hitler and Stalin went through certain time period that TomS did not; and so forth. I say this not to excuse Hitler or Stalin's madness, but to illustrate that it isn't that much more difficult for God to change Hitler or Stalin than TomS. The difference is that Hitler and Stalin were less willing to change for the good, while TomS--in spite of his iconoclastic posts--is a sincere and good man. But there is nothing genetically or "naturally" hard-wired in the Stalins or Hitlers of the world which prevent them from being changed. It is only their own obstinance.
You are falling into the same trap, Tom, that many Christians in history did when it came to heresy. People thought that heretics were irreformable (most times because their heresy was considered or demonic origin); thus, to burn a person to death, or to lock them away, or to exile them, was see as a viable solution. After all, they couldn't change, so better that they be kept away from everyone else. But obviously people can change. Normally, they don't. But they can. Even if sexual perverts were hard-wired in such a way that they could not naturally change, this seems to be a meaningless point if you believe in a supernatural God. Can God create the world, or man, or give us consciousness (or whatever you believe God can do), and yet not heal a man? Anyway, I'm rambling, but the point of it all is that I disagree that people should just be locked away permanently. They should be given the opportunity to overcome their issues, whether it takes 5 months or 50 years. Or perhaps they will never overcome their problems; but in that case they would remain locked up because they did not reform, not because they could not.