But Holmes’s greater good has its limits. Privileging logic, Holmes has little time for civility or compassion. A snob, he dismisses those of lesser intelligence, and his attitudes toward women range from contempt to condescension. Infatuated with the game, he often abuses its minor players. In that first novel, “A Study in Scarlet,” he straight-up murders a terrier. (From an article in the New York Times)
What the hell? The relevant passage from Study in Scarlet:
“Precisely so,” answered Holmes. “Now would you mind going down and fetching that poor little devil of a terrier which has been bad so long, and which the landlady wanted you to put out of its pain yesterday.”
I went downstairs and carried the dog upstair in my arms. It’s laboured breathing and glazing eye showed that it was not far from its end. Indeed, its snow-white muzzle proclaimed that it had already exceeded the usual term of canine existence. I placed it upon a cushion on the rug.
“I will now cut one of these pills in two,” said Holmes, and drawing his penknife he suited the action to the word... "I shall now add a little milk to make the mixture palatable, and on presenting it to the dog we find that he laps it up readily enough.”
It's quite clear that Holmes is using a dog who is already at death's door and due to be euthanized to solve a string of human murders.
Look, I have no problem with people pointing out the Sherlock Holmes is a character with many negative traits, and that some might even construe him as a villain. But every true fan knows he loves dogs.