Twitter has confirmed for me something I've always suspected: humans need to hate and ridicule just as much as they need to love. And even if you created paradise on earth, people would eventually feel compelled to graffiti over its walls.
I don't think humans are a cancer. And I agree that there are many people in this world trying to build and heal. But everyone has a dark aspect, the Jungian shadow, if you will, that is always in danger of undoing the good work.