Santa's Little Helper was forced to watch a video with violent imagery during his training to be an attack dog for Mr. Burns. One of the images in the video showed Johnson picking up his dog by its ears.
Statue of Justice holds a dog by his ears is a reference to Him.
This event really happened on May 4, 1964 on the South Lawn of the White House. Animal lovers were upset when President Lyndon B. Johnson was photographed lifting his beagle, named Him, by the ears to prove to the gathered reporters how much Him like it.