Sahih al-Bukhari 3323--Narrated Abdullah bin Umar: Allah's Messenger ordered that the dogs should be killed.
This Hadith is clear and straightforward, commanding Muslims to kill dogs. However, we must remember that the speaker is Muhammad, who often says things in so many different ways that we can't understand what he means without hearing him speak on an issue numerous times (and even then, we have to go to Muslim commentators to figure out what we're supposed to do). So let's look at another Hadith, where Muhammad tells us that certain dogs don't need to be killed.
Sahih Muslim 55--Ibn Mughaffal reported: The Messenger of Allah ordered killing of the dogs, and then said: What about them, i. e. about other dogs? and then granted concession (to keep) the dog for hunting and the dog for (the security) of the herd, and said: When the dog licks the utensil, wash it seven times, and rub it with earth the eighth time.
This Hadith agrees with Bukhari 3323 that dogs, in general, should be killed. However, it allows people to keep dogs for hunting or for protecting the herd. (We can find some other exceptions in Muhammad's conflicting statements, but they're usually similar to these.)
And now we're back to the killing of dogs in Spain. Are Muslims killing hunting dogs? No. Are they killing sheep dogs? No. They're killing dogs that people keep as pets. Did Muhammad allow people to keep dogs as pets? Not at all.
To recap: (1) Muhammad ordered his followers to kill dogs, unless the dogs are used for guarding a herd or for hunting. (2) Most people who have dogs keep them as pets, not for guarding a herd or for hunting. (3) Muhammad's followers are killing people's pet dogs in Spain, behavior which follows directly from (1) and (2). (4) Kim continues to deny the obvious.