said by RangerTX :

Police will have to provide evidence that it was him that actually posted those kiddie porn and/or that he knowingly enabled someone else to be able to do so.

said by Pirate515 :

Well, to begin with, they will probably arrest him anyway just in case, and when he begins crying and pleading while he's in custody, they will take their sweet time running forensic analysis on his equipment to determine whether his cries and pleadings are legit or not. At the end, he will probably still be punished; however, the punishment will not be nearly as severe compared to what it would have been had he actually posted the stuff.

The point is, kiddie porn is something authorities do not take lightly, and it makes much more sense just to lock up your wireless than to get caught for something you didn't do and then deal with the pain of proving your innocence.

said by Jason Levine :

You forgot one thing. During the investigation, his name will be "leaked" to the media who will go on and on about how a new scary child pornographer was found in the local area. Even if, in the end, he's set free, he'll still been seen as guilty in the eyes of the public. He might even lose his job and have to move just to escape the public "guilty verdict".