Is atheism a belief?

[Belacqua]

I was an atheist before I had any solid convictions about evidence, and even today, questions of whether or not some fucking fairy created the earth..as a gnostic atheist, don't have much bearing on my atheism.[...]

Here is a typical claim about God, which would be familiar to any Neoplatonic Christian, from Augustine to Simone Weil: "All good in the world derives from and ultimately points back to the form of the good, which is God." 

I assume you reject this claim. Would it be correct to say that you find it to be nonsense?

When you reject it (if you do) do you have reasons to reject it? Or do you reject it out of habit, or for no reasons?