Human beings have committed, throughout their history, countless evils – the Holocaust, GULAG, countless freelance murders and rapes, etc. etc. On the other hand, human beings had also created countless great things – the Declaration of Independence, penicillin, heart transplants, skyscrapers and trains. These are morally good things because they enable people to be freer, healthier, or to live better, richer lives where they suffer less. Economic growth is also a positive moral good – it uplifted the condition of many men – we've gotten from farm labor to the cubicle, and frankly, I'd rather be working in a cubicle than working like a medieval peasant and living on rice.
Now, some of us believe that the defining feature of humanity is its capacity for evil. That we are all the relatives of the guys who killed Jesus, who genocided Indians and Gideonites, etc.
Though I am not a Randroid, I do believe Rand was right on this when she believed that this notion was an instrument for the subjugation of man. Consider its extreme application in Leviathan, here, where Hobbes believed humans to be so inherently sinful that we'd supposedly revert to a violent state of warfare if there weren't a mighty government watching over us. A secular application of this is the Lord of the Flies, of course.
Some of us, however, do not believe that evil is the defining feature of humanity. Sure, there are evil people, but most of us aren't. In this notion, we are primarily the relatives of the guys who went to the moon. The guys who built a spaceship in their garage and flew it. Of Bethoven, Bach, Goethe and Mozart. Of Frank Lloyd Wright.
I happen to believe the latter. If you want to believe the former, that's your choice. But I, for one, do not believe myself to be sinful and evil.