There is nothing to explain; this is about the ever increasing level of government arrogance. These people have used their black buggies for many many years and their traditions have been respected. The modesty argument is not some silly loophole they just thought of last week, it's been their tradition for years. Now after many years of tolerance, the government has reached the level of arrogance that they no longer respect the Amish traditions. Anyone with a brain should be concerned about the level of arrogance in American Government with is constantly reaching new highs. Your traditions may be next.
I should have said this in my last post. Thomas Paine, one of the American founding fathers said it best "That government is best which governs least."