Now in terms of here he is, there he is.... there is no tangible evidence for the existence of God as it would be understood in the most basic definition. However, to say that God does not exist because of a lack of evidence is a fallacy. That fallacy is called argument from ignorance. Therefore, the die-hard atheist is practicing a belief system because they believe there is nothing after death. A truly scientific mind would question both view points & contemplate how to test the theory. Just saying....
Some are atheists because they claim that "God does not exist," but in general (probably way over 90%) of atheists only claim that they don't believe there is a God. It's not the same as saying "believe there is no God." See the difference?
1. "I do believe there is no God." - affirmative, active stance.
2. "I do not believe there is a God." - an agnostic stance, passive claim
You're talking about the first stance, the one in affirmative. The second one however is more of an open-ended claim. One that take the stance that "I won't believe in unicorns until you show me that they truly exists" or "Santa Claus probably doesn't exist, but if you can show me that he does, then I will believe." Sort'a thing.
So no, the majority of atheists do no commit the fallacy of argument from ignorance, some do (a few), but not the majority.