No. We don't believe in a god, nor do we believe in sin (which is usually defined as not adhering to the god's wishes). We aren't rebelling against God anymore than we're rebelling against Santa Claus.

Do you not believe in Zeus because you're actually rebelling against him? How about Odin, Thor or Krishna? Like most people, you don't believe in these gods because you aren't convinced they're real, not because there's some rules of theirs you don't like, and somehow trying to pretend they don't exist frees you from them. It would be silly to think I could exempt myself from U.S. law by pretending that the U.S. doesn't exist.

We don't believe in a god because we haven't received sufficient, good-quality evidence that one exists.

A significant overlap does exist between what a religious person would consider a "sin", and what an atheist would consider "bad". For instance, most atheists would be opposed to gluttony, not because some invisible magical man said so, but because it's wasteful utilization of resources that could benefit those who actually need it. Our reasons for opposing gluttony are reality-based.

That can be said for stealing, murder (or violence in general), and other antisocial behaviors.

It's also an attempt to resolve the cognitive dissonance some theists experience when dealing with atheists. These individuals feel that the existence of a god is so obvious that there's no way one couldn't believe in one, so the resolution is that atheists really do, deep down inside, believe in a god, however, they're just in a phase where they're engaged in a youthful rebellion.

It's condescending and false. All we can do is assure everyone that we really do, in fact, not believe. After that, the conversation is merely empty accusations... or it's with people who are apparently telepathic.

It would be like Muslims accusing Christians of just rebelling against Allah because they want to violate Allah's rules. At the same time, the Christians accuse Muslims of rebelling against (Christian)God because they want to violate (Christian)God's rules.

Both cannot be right, however, both can be wrong. Ultimately, the only way to make progress in this conversation is through logic, reason and evidence for any claims made.