To be honest, yes there are quite a few of us North of DC yet South of the Mason-Dixon Line that consider ourselves Southerners. I can't speak for those north of the line or even some of those south of the line, but I do consider myself a Southern Boy at heart. And technically, by the definition put forth by the description of this board, I am a Southerner.
And if there are disputes about MD being a southern state, one of my college professors, a Virginian, as well as further research will tell you that the only reason that MD remained in the Union during the Civil War was because President Lincoln had the MD Legislature arrested to prevent them from voting for secession. About 80% of MD's population were Southern sympathisers.