How about being like Jesus and calling them
white washed tombs
and a brood of vipers?
Believe me, I understand why you, or anyone else, would want to use today's vernaculur when describing these people, but we have to stray away from terms like "idiot," "moron," or the types of words that have 4 letters or less. Trust me, I haven't done a very good job myself at times and I've had to repent of such loose usage of verbal insults.
But, we have to maintain a higher standard than those around us as much as we would like to do otherwise. Now, to use terms like Jesus did, or to properly describe a group of people like He did, fire away.
Did I muddy up the waters enough?