There are always going to be kids who get to watch different movies, tv shows, or play different games. That being said, however, I did loosen the restrictions in our house once Kindergarten started, because I wanted my children to be able to take part in the conversations the other kids were having. I did it once it became apparent that it was hurting them socially not to "know" anything at all about the things the other kids were discussing.
"Loosening restrictions" for us meant allowing some TV-Y7 shows and some video games such as Skylanders and Minecraft; previously I had limited the kids to mainly PBS and educational shows. I do limit their screen time. We also started taking them to more movies, but only "children's" movies.
I have to say that I would strongly discourage a friendship with a child who was allowed to watch the movies you are describing, or even the video games. Our family values would just be too different, and I would never be comfortable sending my child to that families' house for a playdate.
Can you encourage your son to build a friendship with some of the other boys or girls in the class? Can you discuss the issue with his teacher? At our school they do have a social skills pull-out class and lunch group to help the children who need help building social skills.
