I actually brought 50 Shades of Grey up and he had never heard of it. He's just of an age and was a sci fi fan in the 60s, so I think he heard about slash there. And yeah, like cantarina said, I think people, especially from that era, who aren't in transformative fandom do tend to think of slash and fanfic as almost synonymous (he did admit that he's read fanfic before, but it's not his thing - I don't think he has the patience to sift through the crap (and slash) to find the gems).