I visited the R&R HOF a few years ago with my teenage daughter. To be honest, I not a real R&R fan - I'm more of a country music fan, but I did have some favorites during my youth and I wanted to see how the HOF would recognize them. The first thing that caught my eye was the LARGE disclaimer over the ticket counters that warned you that there would be images and displays not suitable for younger viewers inside. I don't seem to recall a similar disclaimer at the Country Music Hall of Fame.
That's because Johnny Cash never had a habit of whipping it out on stage, unlike Jim Morrison and Luther Campbell.