From
http://criminal.findlaw.com/criminal-law-basics/what-is-complicity-or-accomplice-liability.html
"Complicity is the act of helping or encouraging another individual to commit a crime. It is also commonly referred to as aiding and abetting. One who is complicit is said to be an accomplice. But, even though an accomplice does not actually commit the crime, his or her actions helped someone in the commission of the crime.
The concept of accomplice liability means an accomplice faces the same degree of guilt and punishment as the individual who committed the crime. Indeed, accomplices can face the same penalties, including prison time. The key consideration is whether the individual intentionally and voluntarily encouraged or assisted in the commission of the crime, or (in some cases) failed to prevent it"
It is widely accepted that pedophiles are always at high risk of reoffending... Therefore failing to report, is failing to prevent it
And you did say that they should have reported, in your first post