In this would there are horrible people, cruel people, people capable of deeds so terrible that most people would feel sick to their stomachs just thinking about them. There have been great tragedies in this world caused by human greed or jealousy, and even to this day humans are mistreating other humans and creatures.
Yet despite all of this there are kind humans capable of great acts of kindness than most people can ever dream of. There are those who dedicate their whole lives and all their possessions towards the well being of others people or of animals. In the good their are bad, and in the bad there is good.
And yet many times when people act like humans (make mistakes or do stupid things) people keep generalizing, saying humans are a plague of the earth, or I'm ashamed of being human.
But really, you shouldn't. You are not like that crazy person who raped or murdered dozens of people and most people are not like that either. So why are you ashamed of being a member of the human race? Sure we make mistakes, sure we have a capacity for great acts of evil, but those are what makes us human. Our faults and how we deal with them. Embrace your humanity, because for every evil deed, there can be an even greater good deed :)
(Why did I write this? I'm a cynic and a pessimist :/)