I think one of the best proof would be to infiltrate a pedo forum (without ever clicking on the image links) and take note of their vocabulary. If you show this to someone they will go "blaaaaah you typed it yourself" whereas if you show a link to a complete forum with people talking about pizzas and stuff then you will have an easier time to convince people.

But as someone said in the comments, this is a double edge sword strategy as you could be convinced for browsing such forums...I think this is to be our very last proof.