"There is no proof we have child porn groups on Facebook because if you have proof you must be a criminal." <--- There must be a logical fallacy in there somewhere.

If you are going to ban child porn then be logical about it. What happens when child porn is discovered? You need to gather evidence right? Because if it's not evidence based you're just starting a bunch of random witch hunts. So if it's illegal to possess evidence that an entity is trafficking in contraband then it's not really possible to do an investigation and there's no real point of banning child porn in the first place now is there?