Is this material that you want to force drop the same texture for each object in the group. If so you could import the group into a new file and then delete all the shaders for this group until you are left with the default shader and then apply the default shader to your object and its children. You may have to remove all the unused shaders by Edit/Remove unused Masters/shaders in the menu.
  Save the file and reopen it again. You should be left with the default shader for all of your objects , now edit the default shader to what you want. 
 You could try something like this on a test file to see if it works for you .