Safety is relative. Consider that by living in a walkable area avoiding driving, you may be reducing your risk of being one of the ~40 automobile-related deaths a year in the DC region.
You don't have to just worry about murder. You have to worry about rapes, muggings, and property crime. Nobody wants to live in a place where you have to "watch out" or stay inside at night.
Luckily DC has some pretty urban suburbs like Arlington and Alexandia. They are more urban than most of the district. I don't have to worry about my car getting broken into and I can take the blueline to work.
I'd prefer to live in Georgetown or DuPont but that stuff is insanely priced.
What NOVA and Maryland need are more and better commuter rails to DC. The VRE is awful.
(Source: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6128a2.htm)
Also, by including walking in your commute, you are reducing your risk of death from obesity and diabetes, among other factors.
(Source: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2736383/)