To answer your question, sure it's normal, whether people like it or not, we have animal insticts as well.
I used to have a Siamese cat, mean SOB, years ago. The neighborhood I lived in had all sorts of cats roaming around. One day, me and the cat was chilling on the porch, when across the street two cats began fighting. He jumped off the porch and went and jumped right in the middle of it.
Another way of putting it is your "Spidey sense" was tingling
Be nice to your enemy is to be cruel to yourself. - Master Wang (Combat Shuai Chiao) from the EmptyFlower forums.
To locate, close with, and destroy the enemy by
fire and maneuver, or repel the enemy's assault by fire and close combat. ~ Mission of the Marine Rifle Company
What is best in life? To crush your enemies, to see them driven before you, and to hear the lamentation of their women!