Unfortunately, D.C. is so liberal that no libertarian stands a chance of winning there. If D.C. were inhabited by people like the members of this site, but since it's not, he won't win. Unfortunately, in urban areas such as D.C., support for gun control is a winning proposition, even if the person gets caught on tape smoking crack.
You're right. I suppose if the houses of every registered Democrat in D.C. were struck by lightning on Election Day, leaving only the registered Republicans/Libertarians available to cast votes, then he might win.