[...] Why should people who have worked hard and obtained a university degree against all odds be rewarded in the same way as someone, coming from the same poor background, who goes into a life of petty crime?

This argument is correct. We cannot, and should not, explain someone's performance only by the environment in which he has grown up. Individuals do have responsibilities for what they have made out of their lives.

However, while correct, this argument is only part of the story. Individuals are not born into a vacuum. The socio-economic environment they operate in puts serious restrictions on what they can do. Or even what they want to do. [...]