Your question misses the point. Animals may not have the rights we grant a human, some would argue that they have no rights. But that does not mean that we then have the right to treat that creature with arbitrary cruelty. In fact, we don't allow arbitrary violence to be performed on inanimate objects, for instance you might get in trouble for damaging the Statue of Liberty. We decide what we will allow based on our own convictions, morals, customs, religion, etc. Many, likely most, people would agree that torturing animals,even those destined for slaughter, is wrong.