Firstly, even if we accept your argument, your conclusion is false. You are forgetting about the existence of nihilists, these are atheists who doubt everything. You might object to this, so let me explain what atheism is, even though it is pretty self-explanatory. People who are not theists are called a-theists. We know that nihilists are not theists, therefore they are atheists. You conclusion should have been: "Only nihilists can be true atheists."

 But all of your other arguments do not make sense either. You make the same mistake that you are claiming atheists to be making. Let's entertain the idea that without accepting: "laws of logic, truth and knowledge, the validity of our cognitive faculties" we can not be atheists, because every statement we make depends on these presuppositions. What you are forgetting is that this is not exceptional to atheism. Theists, too, can not think without these presuppositions and can not make any conclusion about the existence of god(or anything). Theists have to use their logic before reaching a god, which is unaccounted for at that time. 

 Even if we assume that theists somehow accept god without thinking (yeah, it is impossible), this will not necesarily prove that theists did not make any presuppositions. One could argue that accepting god is a presupposition. 

 Your argument also fails becuse you think atheists have to argue for their disbelief, which is false. The burden of proof lies upon theists to present arguments and proof for god's existence. Atheists do not claim anything. A newly born baby is an atheist, someone who hasn't heard of god is an atheist. Atheism does not need to be an active stance.

 

 Morality is an arbitrary concept. Anyone can say "I'm moral!" and no one can object to that statement even if the person is a child molester or killer. Moral laws are not universal and deciding what is moral or not depends on what moral laws you accept. 

 "Human life is valuable" majority agree with this statement but it is no more than an axiom that people accept without any reason. Why is human life valuable really?

 My point is: If you live according to your own moral laws, you are moral. It doesn't matter what those moral laws are and it doesn't matter where they stem from. 
"Killing is moral." thus, killing is moral.
"Raping women is moral." thus, raping women is moral.
"I am an atheist, but I am still moral." thus, this atheist is moral.

There are stupid people in the world. So why can't there be stupid questions? Calling a question "stupid" does not mean you will not answer the question and inform the the person who is asking the question. Actually, when you be honest and call someone's question "stupid", they will realize how little attention they gave to the subject and they will try to better themselves. If a college student asks what a square root is, I think he deserves being called "stupid".