Why does master Houyhnms finds Gulliver worst then the Yahoo's in appearance?

From the text:

He took up all my clothes in his pastern, one piece after another, and examined them diligently; he then stroked my body very gently, and looked round me several times; after which, he said, it was plain I must be a perfect YAHOO; but that I differed very much from the rest of my species in the softness, whiteness, and smoothness of my skin; my want of hair in several parts of my body; the shape and shortness of my claws behind and before; and my affectation of walking continually on my two hinder feet. He desired to see no more; and gave me leave to put on my clothes again, for I was shuddering with cold.