I've no idea why people are so sadistic. As you've clearly noticed though, some people are. I've seen the same cruelty in Amanda Knox threads, where some people find pleasure in sending innocent people to prison.
I don't think there is really anything to be done about other people choosing to be sadistic thugs. All you can do is try your best to do what is right and oppose the hate, and hope that you're making at least a small difference in the world.