I think there's a basic misunderstanding of the relationship most atheists have with God. Since we think that He doesn't exist, then we have no relationship with Him. That also means that we don't blame God for anything. One may as well blame me for the French Revolution -- I did not exist, so played no part in it whatsoever. The same with God. He does not exist, so plays no part in the state of the modern world.
No -- we blame Humans. In this, at least, atheists are no different from most religious people. I think you must be confusing atheists, "God doesn't exist or is at any rate irrelevant", with antitheists or misotheists, who are actively against either the concept of a God, or hate the one that they think exists.
In terms of the original question: not being able to see God may not disprove his existence, but it doesn't strengthen the case either. And there is a difference anyway between disproving, and providing evidence against -- and not being able to see something does provide some evidence against its existence. How much evidence depends on how likely you were able to see it, though.