I don't see Oates' usage of violence as any different than other writers that attempt to construct settings in which the characterizations of their protagonists can be developed.  Oates does not use violence in a sensationalistic manner or in a way that seeks to desensitize the audience or consciousness, in general.  She uses violence to reflect a part of the modern American setting, something in which her characters find themselves.  The realities into which her characters live are ones where violence is evident.  It would be artificial for Connie to live in a world where there was no violence in the short story, "Where Are You Going, Where Have You Been?"  Oates writes it in recognition of real events in which young girls were murdered.  The idea of an America where murder, rape, and suicide are inseparable to its narrative is what motivates Oates to depict a reality that others might find distasteful.  In her own mind, Oates believes that the artist has a responsibility to depict whatever conditions in which  their characters live and to limit this because of the claims of "violence" is tantamount to silencing the voice of the author.  Oates feels quite passionate about this:

When I point out that, in fact, my writing isn't usually explicitly violent, but deals, most of the time, with the phenomenon of violence and its aftermath, in ways not unlike those of the Greek dramatists.