Quite frankly, I think that any person with these compulsions should be put to death. People with these compulsions are almost never "cured" of them and they cause unimaginable harm to society. A child who has been sexually abused is pretty much ruined as a person for the rest of his or her life. The rest of that person's life is a long, drawn out torture. And this is assuming that the predator lets the child live. Often they are killed by the predator since the crime is so egregious and there is no turning back.
I really, really do not care if the rights of these people were trampled on. Even if my machine was somehow collaterally infected with this malware, it would not bother me in the least if I knew for sure it was part of this investigation.
These "people" are beyond help. There is no reform if you have these compulsions. That is why, even after they have did their time, they must register as a sex offender and be restricted in where they reside. They should just be destroyed.