This is where I disagree completely with your reasoning. There is no necessity to think that a "lack of belief" is a "rejection of belief". "Lack of belief" means "being without belief". The term "disbelief" could possibly be used to express a necessity for contemplation/reason, but certainly not "lack of belief". I, for example, "lack" everything that I don't know about and, thus, don't own/posses, right?
"Lack" means a deficiency
or absence of something needed, desirable, or customary (
http://dictionary.reference.com/browse/lack). In this context, "belief in the existence of God" is "needed" for theism.
And, you can't possibly claim that atheism is the
deficiency of belief in the existence of God, meaning that atheists are those that believe in God, just not enough, right?