As it stands now, if you were to load a bitmap into a map channel on the DX Material, you cannot clear it out using the right-click function available in the other materials types (right-click, clear). Neither can you drag a "none" material channel element over an existing bitmap. Currently, the only option is to clear the entire material from the editor and start again.
What I recommend, is a simple right-click function providing a "clear" option. This will clear out the bitmap in the selected channel.
