A Dog is Still a Dog and Kevin McCarthy is Still a Moron
Dogs- big dogs, mediun dogs, little dogs and dogs that shouldn't be called dogs (the "toy" varieties). Hey I agree someone could easily mistake the variety of dogs for differnt species due to some apparent mating issues. But in reality a toy variety male may catch a Great Dane female in heat, sleeping and successfully have at her. So never say never.
However dogs do show a great deal of phenotypic plasticity, all of which has been brought about by artificial selection. And that would also translate over to mating. We can take eggs from different types of females and successfully mate them with sperm from differing males. IOW science does NOT stop because of physical barriers to a mating issue.
That said, say humans die out and some other intelligent species takes over and starts investigating. If they came across dog fossils they would most assuredly classify the differnt varieties as different species. That just reflects on the classification system. Ignorance allows us to do just about anything wrt classification.
The point? For some reason Kevin thinks that if we call the dog varieties different species, and given the phenotypic plasticity of dogs which has developed over a very short period of time (accepting a 4.5 byo earth*), then that is evidence for macroevolution. Yet macroevolution calls for new body plans requiring new body parts and we do not observe that with dogs. And blind and undirected processes, ie natural selection, drift and neutral mutations, had nothing to do with the dog varieties. That means only dishonest pricks or ignorant poseurs would use them as an example to further evolutionism.
* a 4.5x billion year old Earth relies on the untestable assumption that no crystals survived the accretion process AND that all crystals used for dating the age of the earth were made here, on/ in the earth.