I've actually never read 50 shades of grey... but everyone seems to have this sh!tty opinion of it. haha.
If you are going to be comparing your own gatherings of what BDSM is and comparing it to the book, you should consider that a lot of other people might not have read it either. That might be confusing to them, as well.
If you were to bring up a reference from the book to me, I wouldn't know wtf you were talking about, so the point would largely be lost.