In the context of the article, "animal" is meant to be understood as "something having non-human features". An ugly guy has both human and "non-human" features,

In the context of the article, "animal" is meant to be understood as "something having non-human features". An ugly guy has both human and "non-human" features, so a mind is split in those both directions, and the split evokes the feeling of creepiness. Just because you feel bad about something it doesn't mean it's false.