The way you feel isn't dumb at all! The movie "Sleepers" is the one you saw, and please don't get down on yourself for feeling triggered by it. It's a very disturbing film and the abuse scenes are explicit enough to freak out any survivor. In the book I am doing about the way CSA is portrayed in world cinema this film gets a **** (near maximum) trigger warning.
I hope you will go to your grandfather and talk to him about this. Say how you feel and don't be afraid he will think you're a wuss or anything like that. He seems a sensitive caring man and I know he will want to help you. When we feel badly triggered it's crucial that we not sit alone and isolated.
So far as other films are concerned, you could have a look at the list of films I posted in the bookstore. It's not 100% up to date, but you will see how many films there are out there that specifically and directly deal with the issue of male childhood sexual abuse. All the ones available from Amazon are there, and at the beginning I also have a list of those that are not available from Amazon. It's all alphabetical, so you can find what you want pretty quickly.
Based on your reaction to "Sleepers" it might be a good idea for you to avoid all these films for the time being. Many of them are very good and perform an important service by drawing attention to the issue of CSA, but that doesn't mean they should be watched by survivors struggling with those very issues. There are, in fact, some films that I would not recommend that ANY survivor watch if he is alone.
Nobody living can ever stop me
As I go walking my freedom highway.
Nobody living can make me turn back:
This land was made for you and me. (Woody Guthrie)