These folks are misinformed, or they are afraid that the new measures will actually reduce crime in the District, thereby dismantling their cherished worldview regarding citizens possession and use of arms.
The problem with this -- and it is a huge problem, really -- is: it reduces the Second Amendment to a favor given to us by a benevolent government -- like a parent giving a bicycle to a child. The Second Amendment delineates a RIGHT given by God, or the Creator -- and does nothing but PROHIBIT GOVERNMENT FROM INFRINGING UPON IT. THE DISTINCTION IS EVERYTHING.