Actually the CGC is quite easy and I believe even Ripley could pass it, aggression and all. If a dog pulls on the leash and won't lay down without physical assistance, it isn't well-versed in basic obedience, which is what the canine good citizen test is all about. It's not about temperament, just manners.
I'm all for mandatory temperament testing of all intact dogs. If they do not pass a temperament test, they should be required to be altered. Eventually, the poorly bred dogs would die out, and only the dogs with decent temperaments would remain and breed. That alone, I believe, would help a lot with the problem.
I know, a lot of people say it's all in how you raise dogs, but I think it's mostly about genetics. A dog with sound temperament will not become vicious if it is chained, treated poorly, or ignored. I have seen heartbreaking cases come into the shelter here, dogs that have been severely abused (One dog had to have a leg amputated because her owner beat her with a shovel) and yet some of them are still wonderful and sweet. I am not saying they do not have behavioral problems, but they kept their sweet, loyal nature. Some on the other hand, are downright unmanageable and just plain vicious sometimes. It doesn't mean that they were abused any more severely than the sweet dogs, they just don't have stable temperaments and stressful situations like that cause them to snap.
IMO most of the problems pits have comes from bad breeding. Bad owners ARE part of it, but even in having a bad owner, a well-bred dog will not be a total menace to society as pits are unfortunately made out to be.