Why doesn’t August want his father to call him “Auggie Doggie” anymore?

From the text:

"So, Auggie Doggie," he said, "it was really an okay day?" He got that from an old cartoon about a dachshund named Auggie Doggie, by the way. He had bought it for me on eBay when I was about four, and we watched it a lot for a while—especially in the hospital. He would call me Auggie Doggie and I would call him "dear ol' Dad," like the puppy called the dachshund dad on the show.