Seeking expert counseling is a sign of strength. A personal relationship with a caring professional is proven clinically effective.
Your grandson is at a very young age where he has not yet developed his full ability for cognitive understanding. He DOES know, however, from his peers, that naked women are something that men are supposed to love.
Just watching mainstream television shows him that sexy women, perhaps not naked, but quite provocative nevertheless, are routinely featured and something highly desired by men.
He wants to grow up and be a man as quickly as possible. He has no philosophical or intellectual understanding of the joys of innocent childhood, which have been greatly diminished in our current world culture, and continuing to decline.
He also knows that this "fruit" is forbidden to him, even though it is what is clearly on the forefront of men's thinking, at least as presented on the television, in the magazines that line the checkout counters, in the movies, and on the internet. It is everwhere.
Society tells him this is very desirable but it is also forbidden to him, so it is a forbidden fruit that he wants to have, and that he cannot let others know that he wants to have it. This is a predicament for him.
Computers should be blocked from this material. There are free or inexpensive programs available that can do this.
Here is one site:
He has a dilemma. Instead of confronting him distract him with other toys, non-violent video games, walks in the park, and so on. Limit television that contains too much emphasis on sex, including clothed women, which can be more erotic than naked ones.
Block the computers.
Don't punish him. Change the subject and close down the sources. Punishing a child will only make them more resourceful and adept at hiding things and will have the opposite effect of what is intended.
I am sure that you can effect positive change this way.
I wish you great success and continued kindness and understanding.
Elliott, MAE, LPCC, NCC, CCMHC
I shall keep you and your family in my prayers.