First, let me agree that everything in the kingdom Animalia is, in fact, an animal.

But now let me point out that many of the people who say shit like this might not speak english as their first language. Many languages have different words for animal for different types of animals. I tried to find out what I'm half remembering but I can't find it quickly and I have to get to work. But I vaguely remember that some word that's usually translated as animal into english actually doesn't include insects. Just like the english "deer" at one point in time refered to all wild beasts (but not fish or fowl) and now only refers to Cervidae.