So DC is a little different than most cities. Basically, only downtown is actually DC. All the suburbs are either Maryland or Virginia. A lot of the stats on DC compared to other stats seem crazy because its essentially comparing a city to a state, or a city without suburbs to a normal city. So keep that in mind when reading statistics pages.
I haven't actually lived in DC before, but I've been in northern Virginia (NoVA) for about 2 years now in both Vienna and Arlington and both have been really nice and very safe. DC itself is fun but its a lot more crowded than nova and there are way way way more homeless people. Most of my friends here laugh at me for being leery of the homeless but being from a small town with no homeless at all I just find it a little offputting.