It's not irrelevant to my emotional state while reading those testimonies. I am not saying anyone has <I>proof</I> that Exodus is harmful. I'm not saying there's any solid evidence to that effect. I'm saying that I, personally, have heard enough to make me worry. And I do not want to read the testimonies of people trying to convince me of how happy and thankful they are, not to be gay anymore -- though many of them still aren't what I'd call straight -- while wondering how many of them are now dead.
The sort of control group you'd need depends on the study. If you're looking for a <I>cause</I> of orientation -- i.e., "poor/no relationship with father" -- you need a straight control group. If you're looking to prove reparative therapy isn't harmful, you need a control group of gay people who <I>aren't</I> trying to change their orientation. If you're just looking to prove that it works for X percent of the people who try to change, well, you probably don't need a control group at all. But you have to do your study on a random group of people <I>starting</I> therapy -- not volunteers who report a shift in their orientation for 5+ years, not individuals picked by their respective therapists, just a random sampling of the people who <I>begin</I> therapy. See how many of <I>them</I> report change, or partial change, or whatever you're defining as success.
And it's not the beginning I'm concerned about. It's the end. It's when people realize that it isn't working... after they've invested so much of themselves into making it work. When everything they've been doing to try to "change" has been reinforcing their belief that they <I>must</I> change.
I'm not painting with a broad brush of failure. I'm saying: I don't believe the rosy picture <I>they're</I> trying to paint, because they don't seem to be taking the failures into account. Or trying to find out how many of the failures are in <I>worse</I> shape, psychologically speaking, when they stop therapy. The one person I know who went through Exodus was suicidal, in the end. Not because he didn't want to change, but because, after years of trying, he <I>couldn't.</I>