I've seen this debate pop up from time to time. Graffiti is an element of hip hop, graffiti is separate from hip hop, graffiti pre-dated hip hop, etc. Some say that graffiti has just as strong of ties to punk rock as it does to hip hop.
When referring to graffiti, I'm talking about our version of it. Picking a name and writing it with style on shit, to oversimplify it. Obviously, you can say graffiti has been happening for thousands of years from cave paintings to Viking graffiti, Roman graffiti, Kilroy was here, even bathroom scribbles, and people writing their favorite bands on walls long before we picked it up.
I've also met a lot of writers over the years that feel no connection to hip hop and are about rock, punk, hardcore, etc. and a lot that do feel connected to it.
I honestly don't think there is a definitive answer one way or the other. All of this came together through a series of events involving many people over long periods of time. Is it even possible to answer this one way or the other, or is it subjective from one person to the next?