Well to me guardian doesn't suggest that the animals are being called human, it more suggests that they aren't objects that can be kicked around, if we truly "owned" our animals then we'd be able to abuse them and treat however we feel like.
Animal lovers know you can't mistreat an animal, but people who aren't and aquired an animal anyway see themselves as "owner" and therefore can and do do anything to their poor animal, and are pretty surpirsed when and if the law gets envolved.
So what I'm saying is that the term gaurdian is being seen as different defintions, I guess its all how you view it, but there's no need to jump to one assumption, to one view, and then before anyone else can make up their mind, they read a baised article and see baised opinions.
Let me sum this up for you.
Guardian doesn't tag the animal as a human, just as a creature who needs you.