The fact is none of the stuff you had was illegal. If you plea and don't go to trial they don't have to prove anythng they could try to get you on an old sears catalog of boys in underwear if they wanted and would not have to prove it is porn if you plead guilty. Whereas if you made them take it to court you would have to make them prove that ADULT gay porn and naked kids that are in a book you can buy in a store are child pornography to a jury of adults that would be much harder and you would have a good chance of winning that. Heck they probably knew that and maybe didn't even want to take it to court, they might not have gone through with it if you called their bluff.