"To those who promote this argument, I say breeds of dogs are just different appearances of dogs, but that there are no inherent character differences or temperament differences between breeds."

There are lots of behavioral and medical consequences of genetics. Border Collies are a little OCD; German Shepherds have hip problems at higher rates than other breeds.
http://www.instituteofcaninebiology.org/genetic-disorders-by-breed.html

In humans, northern Europeans get cystic fibrosis at higher rates, Ashkenazic Jews carry the Tay-Sachs disorder at higher rates, and people of African descent are more likely to have sickle-cell. Those are single-gene disorders, which are relatively easy to explain through mutation and historical accidents, like a particular population living with malaria, which selects against "normal" hemoglobin genes.

Intelligence is different. It involves tens of thousands of genes, expressed in complicated patterns all over the brain. The effects of any one are usually quite small. And unlike the sickle-cell gene, intelligence as a trait is useful in many many situations, so that pretty much any environment that we live in as humans (except maybe a super-isolated island) requires that we be as smart as the other humans we're competing against.
https://www.geneticliteracyproject.org/2013/04/15/genetic-expression-in-the-human-brain-the-challenge-of-large-numbers/