They are evolving if the genetic makeup of the population changes. The changes may be caused by human-directed selective breeding, but the dogs are still evolving. The factors affecting evolutionary changes in many organisms are influenced by human activity.
Keep in mind that we can not produce on demand a new trait that we might like to see in a dog (a lab with camo fur) but we can control breeding in domestic animals so that a desired trait that does appear shows up in a large number of individuals in the future generations of that population. You have to use what you have rather than what you would like to have.
Keep in mind also that the different breeds of dogs are generally still able to breed with each other. If they do so the distinct characteristics of the two breeds get mixed together in the offspring and muts are produced.
Edit: I am afraid liberals would taste like what they are full of and would be rather poor eating.
