A prophet orders killing dogs!
They sarcastically said: The prophet of Islam's mercy reached to the extent that he ordered killing the dogs in Madina! Their references were the following:

1 – Ahmad's Musnad, no. 25935. Salem Ibn Abdullah narrated from Abu Rafea, who said: The messenger of Allah (PBUH) ordered me to kill the dogs, so I went out to kill them. I killed every dog till I saw a dog running around a house, I went to kill it when I heard someone from inside the house asking: O you man, what do you want to do? I answered: I want to kill that dog. The person inside the house said: I'm a lonely woman, this dog protects me from wild animals, and predicts the visitors, so go to the prophet and tell him about that. I went to the prophet (PBUH) and told him what happened, and he (PBUH) ordered me to kill the dog.


2 – Ahmad's Musnad also, no, 22745. AL Fadl Ibn Obaidellah narrated from Abu Rafea, who said that the prophet (PBUH) said: "O Abu Rafea, kill every dog in Madina". He said: I found some women from Al Ansar with their dog, they said: O Abu Rafea, the messenger of Allah ordered our men to go in incursions, and this dog protects us, so say that to the prophet (PBUH). Abu Rafea told the prophet (PBUH) about the matter, and he (PBUH) said: "Kill it, Allah protects them".