Whoa, that's quite a
Post hoc ergo propter hoc fallacy. There are probably tons of factors involved in lower crime rates, and I'd really have to see some neutral studies showing a correlation. The kind of people who tend to murder and be murdered have minimal overlap with the demographic that buys guns when a Democrat gets elected.
In any case, DC does have a rather high murder rate (31.4/100,000), up there with Baltimore and Detroit. Still half of what New Orleans has (63.6), and nobody gave me this kind of hassle when I moved there.
In any case, pure murder rates don't really answer the whole question. A lot is neighborhood, demographic, line of work, etc. If I'm in a bad neighborhood but not involved in local drug disputes, not a woman married to an abusive husband, etc. that takes a chunk of the problem away. Still the danger of "spillover" violence, but a lot of the danger is concentrated by demographic.