Animals and Language

I know this is a little off topic from this weeks discussion of zoos, but I have been thinking a lot about language and animals lately. In Carol Adams' piece, "The Rape of Animals, The Butchering of Women", she says that phrases like "treating women like animals" or "pieces of meat" is damaging to the respectful treatment of animals. I am wondering if this is true. To compare a human to an animal is insulting. Animals are less intelligent than humans. We often say things like "you are acting like an infant" or "you're behavior is childlike" when we mean they are being immature. Is this insulting to children and infants? Is it offensive to compare humans to animals when we are insulting their intelligence?