Is this considered animal abuse?

You didn't abuse him, you challenged him. Other animals (I say "other" because, even though many people don't like to acknowledge this, we are animals as well) view being stared down like that as aggression. Not even just "other animals" humans do it too. What would you think if someone got up in your face like that? It's the same thing for many animals, especially apes, our closest relatives in the animal kingdom.