Ok, let me put it another way. Prove the dog was called "Nigger" because Guy Gibson was racist... and "He must be racist otherwise he wouldn't have called the dog that" does not count since that is circular reasoning.
Unless the dog's name came from racist motivations the name itself (and the word) loses racial overtones UNLESS the listener decides to add them again in which case it is the listener who is at fault for assigning motivations the speaker (namer) in this case, didn't have.
Unless the dog's name came from racist motivations the name itself (and the word) loses racial overtones UNLESS the listener decides to add them again in which case it is the listener who is at fault for assigning motivations the speaker (namer) in this case, didn't have.