Precisely, the claims that theists make about their deities - and lets now use the most common sense of the word deity - is that they are ultimately immaterial in nature. That makes it impossible to acquire evidence about them.
How does that lead directly to a lack of knowledge?
But in any case, even if we can call BS on these religious systems, and be pretty confident that no god is going to send us to hell for it, it's still a "belief" and not "knowledge".
Again, no one ever claimed it was.
Now most atheists get very offended when theists say that atheism is a "belief" and argue that atheism is simply a lack of belief based on the lack of evidence.
First, please refrain from commenting on things you cannot possibly know, such as how "most" atheists feel when someone makes a bag argument. You certainly don't know most atheists and cannot possibly have any knowledge of this.
Second, as you are well aware, there is at least weak atheism, which is exactly what you described, and strong atheism. To discuss a particular for, you need to define which one you are discussing and discuss it with someone holding that view rather than conflate the two and then make an incorrect sweeping generalization.
But what I see here is that the lack of belief in this case is in itself a form of belief.
Yes, many people incorrectly attempt to make that argument by conflating different terms, ideas and failing in their logic.
Because what you get from lack of evidence is lack of knowledge.
Also that common mistake is based on ridiculous claims such as this.
And those who claim lack of knowledge are agnostics, not atheists.
And conflating and not understanding the difference between ideas. See exhibit A ^^^