PAIN

 I enjoy fishing and one day I was thinking about how it feels when I have had a hook stuck in my hand.  Then I thought about what drives a fish to go the opposite direction when it swallows the fisherman's hook.  I related it to wanting to be free from what is unnatural to the fish.   
This thought caused me to initiated a conversation with some friends and I was really surprised by one response in particular.  One individual came to the conclusion that fish and or animals do not feel pain as people do.  Although he could not explain how he arrived at this thought but he felt strongly that is the reason, animals like fish seem to continue to fight.
What do you think?  Could this thought be a reason why some can without cause or reason take the life of an animal or even torture an animal?