This does...
“The Department of Public Safety investigated the situation and cleared Gardner of any wrongdoing in handling an uncooperative motorist. He was, however, required to take a verbal communications course before returning to duty.”
Police officers can get away with stuff ordinary citizens would be imprisoned for. The fact he was required to take a course before going back to work means that someone recognized that he was a danger to the public. Hopefully the course taught him something.
I quote from your own excerpt:
"The Department of Public Safety investigated the situation and cleared Gardner of any wrongdoing"