We chose it because the world was shit and we had to. And also cuz he gave us the possibility to choose that.
Not everyone is created with a goodly-thinking brain. Even the stupid person has his point of view - meaning that our brain is not enough to make us differ good from evil. Because we still do not! Only some percentage of us does.
Yes I will blame him because of my humanity. Although, I have always not blamed the creature I had blamed for some time for something after a while... I don't believe you understood this huh.. what I mean is - if I am ill, I blame the parasites at first, but after a while I think, no they're just trying to live just like me. Or if I find someone evil, I think "he chose to be evil" but after a while I am like "maybe he had a sad life, that led to this and this led to this, and he was forced to do evil things and eventually turned out evil, etc. etc."
And yes, it's always us who get the blame :/ which is even more sad.
But don't misunderstand me, I agree that humans are assholes (most of them) but I'm just looking for good reasons for that... and it's not only our fault. I'm pretty sure about that.