Even if that wasn't rather embarrassing, horrific, and illegal (you can't "lock 'em up" for a crime they haven't committed yet), wouldn't it be utterly ineffective? Pedophiles may be physically/psychologically out of whack, but that doesn't mean that they all have uncontrollable urges. Subject them to a test and it's guaranteed they'll suppress their reactions to make sure they pass muster.
Not true at all. There have been volunteer studies on normal / legal sexual images and that is the method used. The brain will route blood to your genitals if you are aroused, you really can't avoid it.
If I recall one was actually about subjecting people to homosexual activity, many people became aroused, yet some did not, so I think it would be a safe basis for eliminating pedophiles from society.
As to why you want functional pedophiles in your society, that's another story for later I guess.
