I think they have a problem with it because video games are for the most part intended to be for kids. Adults can play them but for the most part they are made for teenagers on down. While movies that depict sex or graphic sex are for the most part made for adults.
I am sure if they started showing sex on television shows intended for youngsters you would hear quite an uproar also.
Anyway, just one final comment on that scene. I would think if they were going to make a scene like that they would want to make it with graphics that were not 10 years old. Not sure if it was just the video I was watching it on. But the graphics I saw looked ancient.