Why are humans so cruel to animals?

I was recently reading about the passenger pigeon and how it went extinct because of humans hunting it for meat. I read on the article that people would take one pigeon and sew its eyes shut with a thread and needle and then use it as a decoy to attract other birds. Then when the others birds would land by it, the people would throw nets on them and then to kill them, they would crush their head with their thumb and forefinger. Seriously, WHAT THE ****?!?!? This pisses me off so much. This is absolutely horrible and cruel. What are you opinions