Unwinds are dangerous for a couple of reasons; the first is that they are more than likely troublemakers to begin with. There is a reason that parents have designated a child as an Unwind. In Connor's case, he is a borderline juvenile delinquent. He gets terrible grades in school, and he's a general troublemaker. His parents are at their wits end with him, and they see unwinding as a way to be done with Connor and provide for many other people. This makes someone like Connor dangerous because he knows that he has nothing left to lose. If he is caught, he dies; therefore, running and fighting back are his only two options.
Unwinds are kids that have been backed into a corner, and most animals fight hardest when put into that position. Unwinds are also dangerous because they share the same plight. This gives them an immediate bond that allows them to want to work together and protect each other. There are also quite a few Unwinds, and strength comes in numbers.
Unwinding isn't a weird process anymore. It is looked upon favorably by most of the population, and it is seen as a simple and viable solution to the problem of delinquent children. Putting all of those kinds of kids together in a single location is a dangerous proposition because it is now a large group with nothing left to lose.